Match your goal: if you need to roll/mold, prioritize almond paste or a ground-almond+powdered-sugar paste; if you just need almond flavor for baking, frangipane-style cream works.
Use the listed ratio to replace marzipan by weight; if your substitute is softer or wetter, start with ¾ of the amount and adjust after mixing.
Tune texture: add powdered sugar to thicken, or a teaspoon of milk/egg white to loosen until it holds shape.
Taste and finish: add a few drops of almond extract (or a pinch of salt) only if your substitute tastes “off” compared with marzipan.
Proceed with your recipe: chill 10–15 minutes before rolling if needed, or spread immediately for baked fillings.