When I stopped being able to eat gluten, I began researching everything about it, and I discovered a few things. First of all, just because something says it is gluten-free does not mean it is tolerable or good for everyone who can't eat gluten. You still have to figure out what is good for you. I also can't eat rice or any products made with rice or rice flour. That left most of the gluten-free recipes, mixes, and other products right off my food list because rice flour is the go to flour for most gluten-free and celiac foods.
Fortunately for me, I can have gluten-free oats and oat flour. My favourite is the brand you see above—Only Oats. If you don't have access to oat flour, you can also grind your own using quick oats in your blender until it is fine. I have done much experimenting with oat flour. One of the things I like best is that oats are a familiar flavour in baking already, so it is more likely that other people will also like it. I think it is so important that you can bake things you feel confident serving to someone else. And I have done a lot of taste testing to rave reviews in some cases.
So here are a few tips I offer if you want to adapt a "regular" recipe to one using oat flour. And I will mention that I never use any kind of gums to make up for the lack of gluten, and I don't use other gluten-free flours in addition. These tips are for substituting only the oat flour for all of the wheat flour.
Always weigh the oat flour.
A regular kitchen scale works fine for this. If you are grinding your own, and it calls for 200 gm oat flour, weigh out 200 gm quick oats, or old-fashioned oats, and grind that. Never scoop oat flour out of the package with a measuring cup—Oat flour compacts, and you will get more flour than you want by doing that. Actually, a pastry chef I know also always weighs out wheat flour so that he gets a consistent result.
Use less fat!
Oat flour does not absorb as much fat of any kind as wheat flour. Therefore, I always cut the amount of fat (butter, etc.) to about half what the regular recipe calls for, and go from there. For instance, when I bake a cookie recipe with 300 gm of oat flour, I only use 1/2 cup of butter. Cookies are a great way to start substituting oat flour for regular wheat flour. They are so forgiving compared to something like cake.
Use less liquid!
If a recipe calls for liquids—or liquid like ingredients such as milk or sour cream—you will more than likely need to use less of that because eggs are also a liquid. Room temperature oat flour soaks up liquid like a sponge, and then doesn't act so nice. I had a favourite soft ginger cookie recipe that called for 1 cup honey, in addition to 1 cup sugar, and a bit of molasses, and two eggs. I wound up decreasing the honey to 1/4 cup, and using only one egg, but keeping the other amounts the same, and the recipe turned out just like the wheat flour recipe. In fact, one little taste tester told me that they were better than her Mom's. I considered that a great compliment
Use oat flour cold
And now here is something I discovered only recently, and quite by accident, but has made a huge difference. Do not use oat flour at room temperature. Store it in the freezer, and use it straight from the freezer. For some reason, oat flour absorbs liquids very differently when it is very cold than when it is warm. When you use it warm, particularly with any kind of liquid, it is impossibly loose, and kind of slimy, and does not cooperate—and adding more flour doesn't help. However, if the flour is cold, and you use the liquid straight from the fridge (eggs can still be at room temperature), then the difference is amazing.
I hope you will find these tips helpful, and that you will do some experimenting on your own. I have made cookies and brownies, and other kinds of squares. I have even made cream puffs, and more recently a mug cake. I use butter and eggs in my recipes, because they are not a problem for me. Even so, I believe these tips will help you even if you can't have that because I hope they will help you understand the way oat flour responds.