mac & cheese
A Bechemel Sauce is 1 Tbsp plus 1 tsp flour, 1 Tbsp fat like butter or margarine and 1 cup milk (dairy or non-dairy). You can make substitutions for each of these items.
Gluten free flours like brown rice, buckwheat, potato, sorghum, and millet flours will all work as substitutions. Keep in mind that without the gluten, these flours do not get as sticky, so you may need to add additional flour and cook a little longer to get the consistency that you are desiring.
You could add about 2 Tbsp cornstarch or tapioca to your flour for extra thickening.
You can also prepare a mac & cheese sauce using raw cashews which is rich and creamy. No flour necessary:
Soak 1 1/2 cup raw cashews in water in the fridge overnight. Drain and put in blender. Add 3 Tbsp lemon juice, 3/4 cup water, 1/2 tsp chili powder, 1/2 clove garlic, 1/4 tsp turmeric, 1/2 tsp mustard. Blend until smooth. No need to cook.
I hope you find this helpful.