I used to have a standup clothes hanger in my backyard, that I recently
removed. It was attached to a cement base that was embedded in my lawn. I
want to take out this base, that looks to be around a foot deep, and 10-11
inches in diameter, but once I do that I will be left with a big hole in the
lawn.

What should I fill the whole with to be able to grow grass on top? DO I
need to add anything, particularly at the bottom of the hole, before I add
soil?