Preheat oven to 350F.
Pulse oats, pecans, almond flour, sugar, and cinnamon in a food processor for 5-6 one second pulses. Add butter and process until mixture starts to clump. Put the streusel in the refrigerator while you make the filling.
Core and thinly slice the pears. To slice pears by hand, cut them in half lengthwise, core them out with a cookie scoop or a spoon, and then slice them no more than 1/8 inch thick. If you have a slicing spiralizer, attach the pear to the spiralizer, choosing an attachment that will core the pear as well, and run it through the spiralizer.
Combine the pears, ginger, cinnamon, and bourbon in a large bowl. Put the filling into a casserole dish, distributing it evenly. Top with the streusel mixture. Bake for 50-60 minutes, or until the top is browned and the filling is bubbling. Serve with vanilla ice cream.