Shell your acorns and remove the papery "test," the skin on the nuts. If you're using dried acorns, soak them in water overnight. Once the acorns are soft(ish), i.e., soaked overnight or fresh, grind in a food processor or meat grinder until they are the consistency of stone ground corn or even a bit larger.
Move the acorn grits to a large container and cover with water. Keep cool. Change the water once or twice a day for at least five days. Taste the grits for bitterness. They are done when they are not bitter.
If you want to do the lye treatment, add the tablespoon of lye when the acorn grits have lost most of their bitterness, anywhere from five to 10 days after you started leaching them. Stir in the lye and keep everything cool. Let the acorn grits sit in the lye water 12 hours or so.
To remove the lye from the water, pour out the lye water, then refill the container. Repeat this a few times a day until the water is mostly clear, about 3 days.
Store the grits in a jar of water in the fridge, or dry them. Dried, they will last indefinitely.
Notes
NOTE: If you are doing the lye treatment do not use aluminum containers! You will poison yourself. Plastic, ceramic and stainless steel are the way to go.