If adding a flavoring, mix it in completely to the applesauce.
Line 3-5 dehydrator trays with parchment paper (not wax paper or foil) or sheets specifically made for your dehydrator (this is preferred).
With an offset spatula, spread the pureed mixture smoothly and evenly on the trays, leaving at least an inch all the way around. The puree should be about 1/4" thick (the thicker it is, the longer it will take to dehydrate, but the thicker your final product will be). Use the flat side of the spatula to create flat edges.
If your dehydrator has temperature settings, set to 110°F (or the lowest setting) and let dry for 8-12 hours. Check periodically after 8 hours. The edges will dry first. Rotate trays if needed to ensure even drying.
When you are able to easily peel the fruit leather completely from the trays, remove from the dehydrator and place on a parchment sheet (or use the one from the dehydrator if you didn't have dehydrator sheets). Using kitchen shears or clean scissors, trim the edges and cut the fruit leather into 2" strips (while still attached to the parchment). Roll and secure with tape or twine.
Store in an airtight container at room temperature.