Hydration numbers aren't that meaningful by themselves -- whether an 80% hydration level can produce a high-rising free-form loaf will depend on a lot on the types of flours or grains that are used. (Usually, 80% hydration is most appropriate for flatter or roughly shaped breads: ciabatta, focaccia, pizza dough, rustic baguettes, etc.) With the specific mixture of spelt and "strong white flour" (high protein) you mention, it should be possible to get a loaf with a little more lift. But it's hard to say for certain -- the flour itself will affect whether it's actually possible to do what you want.
Frankly, there are a lot of variables that could be creating problems beyond the ingredients. A sourdough culture that produces a lot of acid quickly can make it quite difficult to get a tall loaf. Or, if your sourdough yeast is weak and takes more than a couple hours for each rise, you might be producing too much acid. The acidic environment will tend to weaken the gluten, and you'll inevitably get a loaf that spreads. If this is the problem, you'll need to refresh the starter with a few closely spaced builds that really dilute the starter (e.g., dilute your starter 1:4 or even more with new flour/water in each build). That will strengthen the yeast but cut down on the early development of acidity. Unless you're a sourdough expert, I might actually suggest trying to get good results with regular baker's yeast in your recipe before doing the sourdough conversion, since the sourdough may be contributing more than anything else to the spreading.
If the starter isn't the problem and the ingredients can hold up the loaf, the next options are alterations to technique. The best suggestion I can give is to introduce "stretch-and-fold" maneuvers into the first rise. After you mix the final dough (which doesn't necessarily need to be heavily kneaded), come back every 30-45 minutes or so and stretch the dough from each side at a time. Pull out, lift up, and fold on top of the rest of the dough. Do this from each of the four sides of the dough. Let rest for 30-45 minutes again and repeat as often as you need until you feel the dough strengthen significantly.
If you adopt stretch-and-folds, you may not see the same amount of rise you saw without them, so you need to just keep your eye on the clock and use the same amount of time you did before for the first rise. By the time you reach the shaping phase, the dough should be much more taught and elastic.
The other significant issue is shaping. Do you do a pre-shape and bench rest before the final shaping? That can also help. Preshape by pulling the dough taught, folding in upon itself a number of times, then let rest for 15 minutes or so before doing final shaping. Basically, the more times you stretch the gluten and let it rest, the stronger the dough will get -- whether you do that in folding during the first rise or in a preshaping before bench rest, it will help. The shaping technique itself can also significantly affect the stability of the final loaf (but that's hard to explain in a text response).
Also, you may be waiting too long in the final proof if you wait to fully double in size. Unless the sourdough culture is very strong, you might have better results by waiting for only a 1.5 or 1.75 rise. If you do that, you may want to be somewhat gentle during the final shaping to preserve some of the gas from the first proof.
In fact -- if all of this sounds way too fussy for you, another option may be to skip all the stretching, folding, shaping, etc. and avoid the final rise almost altogether. Let the dough roughly double in size during the first rise, then shape very gently into a rough ball, rest just a short time until it starts to expand again (no more than an hour or so), and then throw it in to bake.
Lastly, the baking method could change things. If you're baking on a flat stone, the dough can just spread significantly during baking itself. I've sometimes seen this with high hydration sourdough -- I load it on a peel, and it looks okay before it goes in the oven, but during the oven spring phase, it just becomes wider instead of taller. Baking in a pot or round pan could help to restrain that spreading a bit without making it look too much like bread from a pan. And, if you cover a pre-heated pot for the first 15 minutes or so of the bake, it will help the oven spring and crust development.
It's hard to know which of these options will work best for you, since there are a large number of issues that could be at fault in this case. In my experience, however, the two most likely causes for spreading are a weak sourdough starter or inadequate strengthening of the gluten during shaping.
Gluten is a protein that gives bread elasticity. Water makes gluten spirals relax, and kneading helps stretch the gluten and connect with other gluten strands. Bread that lacks stretchiness:
- may not have enough gluten to start with. If you are using a low gluten flour then you won't get and elasticity. In general any plain white flour will have enough, but for best results use bread flour, also known as strong flour
- may be too dry. Gluten needs water to relax and stretch, if your dough is too dry, or "tight", then you won't get good elasticity
- may have not been worked enough or worked in the wrong way. Kneading mechanically stretches gluten, if it isn't kneaded enough, or the technique isn't right, then no elasticity
- may not have been risen enough. Yeast actually improves the dough, it really works on the gluten. Rise isn't just about leavening, it makes a big difference in elasticity. You should notice a big difference if it's been risen enough
If I had to put money on it I'd say it's probably your dough being too dry. This is an easy mistake to make, you turn your dough out on the counter and it's really gooey, must not have enough flour right? But as gluten get worked it uses up some of the extra moisture, so adding too much flour at the beginning will rob the gluten of the water it needs to relax. Kneading with oil instead of flour may help there.
As an aside, I generally add a couple of tablespoons of olive oil to my pizza dough to improve flavor and texture although that's totally optional. Also, you didn't list salt as an ingredient, bread needs some salt, many bakers recommend 10g per 500g of flour, although I usually cut that down some.
Best Answer
If bread falls after you score it, it's because the bread is overproofed. Basically, the bubbles of carbon dioxide have reached the largest size that the structure of the dough can support and the stress of scoring causes it to collapse. They key is to either score it earlier and let it continue rising a bit, or to score & bake it earlier (this works great if you have a very hot oven and can find a way to get some steam into it).
If your neighbor came over with bread and it flattened in your oven, it's possible that hers also overproofed in the time it took to transport it (or the extra jostling of transportation caused them to fall).