What to do with leftover almond peel

I have had some luck with other oily nuts by grinding them down into semi-large pieces, and then letting them dry out on a flat cookie sheet. Then, step-wise, grind iteratively, with dry steps in between. If you can do this one time with a lot of product, you can save some in an air tight container for next time.

Generally, there is no reason not to use it. However, I'm hard pressed to think of a good place, generally because good cooking prefers other, stronger flavored liquids instead of water.

An application where you can have the flavor on its own would be making ayran or a lassi. I think it would be an improvement over plain-water-ayran.

For other uses, just substitute plain water to get a slight nutty hint. I like to pair rice with nuts, so you could use it instead of pure water to cook rice. Or add it to a pot of stock you are making - with a complex stock of a meat and several vegetables, it will be too subtle a taste to register consciously, but will enrich the flavor as a whole. For a simpler stock (e.g. just chicken with classic mirepoix) the taste of almonds can get too strong, depending on the quantity you use.