Can I substitute ground nuts in place of flour in a cookie recipe?

Planning to use ground almonds. Recipe uses 1 stick of butter, 2 eggs. I still plan to use mostly regular flour, I wanted to sub just a little of it with ground nuts but I never thought about almond flour.

If you want soft and chewy, it will be difficult to attain that texture with ground nuts. What nuts are you wanting to use? Almond flour behaves the best, in my opinion- but you will still need to use some flour to keep the desired texture. What is the fat in the recipe? You can usually make a cookie softer, longer if you use half butter, half shortening instead of all butter. Are eggs the binder? How many?

I'd specifically look for a recipe that uses nut flour and study the ratio. Try the recipe as is and then play around with it if it needs changes.

Recipe calls for 2.5 c of flour & produces a really soft, chewy cookie. I hate to use the ground nuts to get the flavor I'm looking for and the cookie turns out crumbly or firmer. I definitely want to make sure it stays soft and chewy.

It really depends on the type of cookie. In some recipes it would give you a tasty result, and in some it might not be a good idea. What is the total amount of flour in your recipe? Nuts have natural fats in them and will absorb less liquid than flour would, so it would be best to adjust the amount of liquid ingredients as well. I'd say in about 70% of cookie recipes you can successfully incorporate ground nuts. You could also use nut flours, which are finer and have lesser fat content and behave more like flour, except for the fact that they contain no gluten and have no binding ability, which produces more crumbly cookies.