Puree all the ingredients together. You can leave the skins on the peaches and apples if you want, just make sure to puree them very well and add water if the mixture is too thick. You should be able to drop a spoonful of puree and still see the shape of the drop and then shake the pan and have the surface of the puree be smooth. I puree my fruit in a pot with an immersion blender and then I warm it slightly before spreading it in my dehydrator, but that isn't necessary, I usually do that because I use frozen fruit.
Spread evenly over the sheets in your dehydrator and dehydrate about 8 hours but this will depend completely on how thick your fruit puree is, how wet the puree is and how hot your oven or dehydrator is. Or spread on a rimmed baking sheet lined with wax paper(or brushed lightly with oil) and bake in your oven on the lowest temperature. After spreading the mixture out I give the pan a shake to smooth the surface out. Make sure to rotate your pans every few hours once they're in the oven and switch them if they're on different racks. I even needed to switch the order of my shelves in my dehydrator. Make sure to check the leather frequently near the end regardless of whether you use the oven or a dehydrator as you want it to be barely dried and not crispy. Remember it will be firmer once it's cooled too.
If your fruit leather is still sticking to the pan or ripping in places because it's too wet and not lifting off in one large piece then return it to the oven to dry out some more. Once the leather is done, remove it from your sheet and slice using a pizza cutter or a large knife and roll in wax paper or parchment paper and secure with an elastic. If storing for a long period of time you might want to keep them in the freezer. They thaw very quickly so just leave them on the counter for 5-10 minutes before unrolling.