Preheat oven to 425°F. On a lightly floured surface, stack two pie crusts on top of one another (or roll homemade double pie crust dough) into a 12 x 18-inch rectangle. Use a ruler if necessary to ensure size. Lay into a 9 x 13-inch pan and work it so that it's firmly pressed into the bottom and up the sides with some overhang on the edges. Use a pie crimper to remove the overhang and use small cookie cutters to cut shapes from the overhanging scraps if desired. I have cut hearts, but you could do stars, fall leaves, flowers, etc. Set all aside.
In a large bowl, combine strawberries and apples with lemon juice. Add sugar, cinnamon, nutmeg, ginger, flour, and almonds and stir well to combine. Gently fold in the mixed berries. Transfer the fruit mixture into the prepared crust in an even layer. Whisk an egg and use a pastry brush to brush the pastry cutouts if you've made any and exposed edges (and walls) of the crust.
For the oatmeal crisp topping, combine all ingredients in a large bowl EXCEPT for the melted butter. Whisk everything together. Pour cooled melted butter over the mixture and use a pastry blender, a fork, or your fingers and mix and squeeze into clumps at the same time. This process ensures you will end of with varying sizes of oat topping, from sand to big clumps.
Scatter over the fruit filling. Arrange the pastry cutouts to be 'tucked in' here and there in a playful pattern on the crispy topping and sprinkle the entire top and cutouts with raw sugar.
Bake for 35 minutes BUT check at the 20-minute mark for browning. I recommend placing (not wrapping, just lay it over top) a sheet of aluminum foil over the dessert if it appears to be browning more than you'd like it to. Finish baking for the remainder of the time. Remove from the oven and place on a wire rack to begin cooling.
Because of the size, this dessert will take at least one hour to cool to the point of being able to serve it warm. Serve with vanilla ice cream and/or garnish with additional sliced or whole strawberries or mixed fresh berries.