While reading your question it sounds like: 'How can I make a salad without the ingredients to touch each other'. So I think what you actually wants is not possible.
So if you want all of your 3 points to work for, I would suggest you don't make a salad, but serve the chips/cheese separated from the rest of your ingredients. Also, then you can mix the ingredients easily such that your dish does not get plain at the end.
Maybe it won't look as nice as you want it to look, but it's about taste in the end isn't it! So just:
-Serve the chips/cheese separated from the rest of the salad
-mix the other ingredients such that your dish does not get plain near the end. (I would say, except for the sour cream, you don't want that to be fully mixed with the other ingredients)
-I also think that serving your chips separately gives you the change to eat them with some side dishes, like guacamole or a salsa.
If you really want it to be a salad, you can maybe make smaller portions, so give every person it's own plate. Then there is in total more 'edge' on all plates together to put the chips on, there they will become get less soggy. Also a personal plate will be less 'deep' and so you won't have the problem of getting a plain dish at the end. You can put on the cheese afterwards at the table, so it is not already melted before being served.
To assemble a burrito:
Traditional method
Lay your tortilla down on a flat surface
Spread a layer of the first filling (perhaps rice) down the center of the tortilla in a little row, about 1/4 the width of the tortilla, leaving about 1/4 tortilla width on both ends for the folding. Something like this:
![enter image description here](https://i.stack.imgur.com/I29Qgm.png)
Spread a layer of the second ingredient (such as beans) on top of the first ingredient.
Repeat step 3 with each subsequent ingredient.
Fold up the tortilla.
Obsessive Method
Combine all filling ingredients in a bowl and toss, as you would a salad, until they are uniformly distributed.
Spread down the middle of the tortilla as indicated in the diagram above.
Fold up the tortilla.
Tips for Success
Make sure the filling ingredients are suitable for being uniformly distributed. For example, don't use large slices of avacado, use a dice.
Folding
Take one side of the tortilla (as indicated in the diagram above) and fold it over the the edge of filling towards the other side. It can overlap the filling and other side a bit.
Fold both the top and bottom of the tortilla over the filling at the edge of the filling.
Starting with the previously folded side, roll the burrito until it is a single role.
Place seam side down on the platter or pan you will heat it on, top with sauce or cheese as desired, and bake.
Consuming Burrito
Eat it. However you want. Enjoy the variety of flavors and textures the distribution of the filling provides.
Best Answer
There are many variants of sour cream. I am not quite up to date on the naming of dairy products in Belgium, but don't you find sour cream labeled as "zure room" (Dutch) or "crème aigre" (French)?
Mexican sour cream (Crema Mexicana) has however a higher fat content than the sour cream commonly available in European countries. A close approach is crème fraîche, but it might not be just as sour. If you want to make it yourself, you can add living bacteria culture (e.g. from yogurt) to heavy cream (fresh cream with >35% fat) and keep it at roughly 37°C until it reaches the required thickness.