Melt 3 tablespoons of margarine in a large skillet on low to medium heat. Add the flour to the margarine and stir until they are thoroughly combined. Add 1/2 cup of water to the flour & margarine mixture and stir until the water is almost absorbed. Continue to add small amounts of water as you stir (about 1/4 cup at a time) until the consistency becomes like a thick sauce. NOTE: Make sure the stovetop temperature is halfway between low and medium.

Mix the spinach, salt, and onions in a heat resistant mixing bowl. Add the sauce to the mixing bowl and stir thoroughly. Place the mixture in an oven safe casserole pan and bake at 350 degrees for 20-25 minutes. Serves 4.