Cream butter and salt in bowl.
After a bit of creaming, add sugar. Beat until it's nice, light, and fluffy.
Mix in vanilla.
Should look like a nice buttercream at this point.
Add in flour (mix on low)
Then, form the dough into a rectangular prism. Knead it, push it together, ideally there should be no cracks inside. Can plop it down on the counter to get nice, even sides (spread some flour first).
Wrap the brick in plastic and chill.
Once chilled, cut in uniform slices
Bake for 10 minutes at 350 degrees.