Match intensity first: if you want the same bold almond aroma, choose amaretto or almond oil; for a gentler effect, use vanilla plus a tiny almond essence amount.
Use the listed ratio and mix substitute in with the wet ingredients so it distributes before baking.
If your substitute is wetter (amaretto) or thicker (marzipan/almond butter), adjust batter consistency with 1–2 teaspoons of liquid or a small flour increase.
After baking (or if making a no-bake base), taste and fine-tune: add a few drops more if mild, or dilute with a bit more base if too strong.
For almond oil, start tiny and build—its flavor can become bitter fast if you overshoot.