Crumb-Topped Apple Slab Pie

INGREDIENTS

box ((14.1 oz) refrigerated pie crusts (or sub homemade pie crust dough))

1/3 cup

granulated sugar

1/3 cup

packed light-brown sugar

1 cup

quick oats

1/2 cup

all-purpose flour

1/4 tsp

salt

1/2 cup

unsalted butter, chilled and diced into small cubes

1/3 cup

granulated sugar

1/3 cup

packed light brown sugar

3 tbsp

all-purpose flour

1 tsp

ground cinnamon

1/4 tsp

ground nutmeg

1/4 tsp

salt

1 1/2 tbsp

fresh lemon juice

lbs peeled (, cored and thinly sliced crisp apples (see notes))

1 cup

powdered sugar

2 tbsp

half and half (, or more as needed)