Practice making gravy a few times before you do it on Thanksgiving Day. Either throw the test mixture away when you are done or add spices and use it but make it a few more times to get the hang of it.
2 tbs oil
2 tbs "all purpose" flour (some other flours won’t work)
2 cups water
Heat the oil in a sauce pan and gradually add ¾ of the flour. Watch how the flour looks dry when you add it then becomes moist as you cook it. Add the rest of the flour and let it simmer until it is liquid again.
Fact 1, Flour does not mix with oil. (Apply this thought next time you make pie crust.)
Cook the flour until it starts to brown. This is what helps make the gravy taste good. Keep stirring and be careful not to let it burn. This is called a “roux”. Save about 1/3 of the roux in a cup.
Fact 2: Browned flour tastes a bit nutty and no longer tastes like flour.
Add the water at a low heat setting and slowly stir the mix. Watch as the flour expands. Keep adding the water to stay ahead of the expanding. Since this is only an experiment, add more water if you like but not more than 1 cup or so. If you water it down too much, add back some of the reserved roux. Increase the heat. Watch as it continues to expand. Keep stirring until you like what you see as a gravy. Gravy will continue to expand even after it is in the gravy boat and on the table being served.
Fact 3: Flour expands in water and more so in hot water.
This test recipe makes a very bland gravy but it should not taste like flour, this is the most important point that lets you know when you have cooked it enough. Gravy is grainy, otherwise it would be a sauce.
When you want make a real gravy from the oils and broth from pan drippings, be absolutely sure that only oil is to be used in making the roux otherwise you will start the expanding process and it will become more difficult to cook.
Pour the drippings into a measuring cup and let it stand for a few minutes. Broth will drift to the bottom and the oil will be on top. Use a baster to siphon the broth from the bottom. Remove some oil with broth if you have to but be sure to prevent any water from getting into the roux.
If you use the same pan that the turkey was roasted in you will be cleaning the pan as you make the gravy. If you have any broth in the freezer or from boiling the giblets, use that instead of water.