Normally in a square grid such as a 5x5 grid
the way to accomplish this would to be to remove only 4 squares such that no two touch the wall of the grid, nor do they touch one another
This has a very similar arrangement even when you reduce the size of the overall grid by 1 row and/or 1 column
What I'm trying to figure out is how few squares I could remove from an irregular shape
or one with squares already removed in order to stop any 2x2 square from being possible.