Maybe use a food processor to get granola crumbs that you combine with melted butter. Press most of it into the bottom of the pan to make a crust. Bake 10 minutes. Top with your fruit. Sprinkle with the remaining granola - combined with some flour and egg to make sand-textured dust. Drizzle with more butter, so the topping technique is similar to Willies Crisp.
Or take a look at this oatmeal jam bar recipe RStuart recommended a while back. And use your granola (perhaps ground a bit) in place of the oatmeal. https://www.thespruceeats.com/one-bowl-oatmeal-jam-bars-4843487
