Match the recipe goal first: use a neutral option (brown rice flour) for light flavors or a body-rich option (buckwheat flour) for better structure.
Start with the listed ratio (often 1:1); if the substitute is denser (sorghum) or lighter (rice), adjust by adding 1–2 tablespoon liquid per cup batter as needed.
For baking, check color at the lower end of the bake window—quinoa-like flours can brown quickly, especially oat flour.
Let batters rest 5–10 minutes (especially with rice or sorghum) so the flour hydrates and reduces grittiness.
Taste/texture test: if the crumb feels dry, add a tablespoon of fat (oil/butter) or an extra spoon of liquid next time.