Prepare the crockpot by greasing it with cooking spray or butter.
Boil the macaroni according to package instructions until al dente.
Drain the pasta and return it to the pot.
In a saucepan, melt the butter over medium heat.
Whisk in the flour to form a roux, cooking for 1-2 minutes.
Slowly pour in the milk while whisking constantly.
Continue cooking the mixture until it thickens slightly, stirring frequently.
Stir in the garlic powder, onion powder, salt, and pepper.
Remove the sauce from heat and add in the cheeses, stirring until melted.
Pour the cheese sauce over the macaroni and mix well.
Transfer the mixture to the prepared crockpot and cover.
Cook on low for 2-3 hours or on high for 1-2 hours, stirring occasionally.
Once done, serve from the crockpot and let guests create their own mac and cheese bowls.