Roll out the bottom pie crust and gently place it into a 9-inch pie plate. Add the homemade cherry pie filling, spreading out evenly into the pie plate.
Roll out the top crust large enough to cover the pie with a bit of overhang. Gently place the crust over the pie. Trim the edges as needed and/or tuck excess pie crust under, then use your fingers to crimp and seal the edges of the pie. Use a sharp paring knife to cut slits into the top crust.
Alternatively, you can cut the top crust into strips to create a lattice crust for your pie.
Whisk together the egg and water. Lightly brush over the top crust. Sprinkle with granulated or coarse sugar.
Place on a rimmed baking sheet and bake for 40-45 minutes, or until the crust is golden. I recommend checking the pie after 20-25 minutes and tenting it with foil if it is getting too golden too early. If only the edges are getting dark, you can gently cover the edges with foil or a pie guard.