Choose the substitute based on your goal: closest wheat performance (whole wheat or all-purpose) vs. flavor/crumb differences (kamut, einkorn, rye, or gluten-free).
Replace spelt flour using the listed ratio (most are 1:1; rye is ¾:1; gluten-free is 1:1 with xanthan).
Mix and check consistency: if dough/batter seems dry, add liquid 1–2 teaspoon at a time; if it’s wet/sticky, add flour 1 tablespoon at a time.
If baking, let the dough/batter rest (10–20 minutes) before shaping or baking to improve hydration and texture.
Bake as directed, then taste-test one small portion next time to fine-tune water absorption and bake time for your chosen flour.