I knew sows make nests before they farrow. I didn’t know they spend so much time and effort on their nests after they farrow.
Look at this gilt raking the bedding with her front foot. The bedding was more or less even, but she took one side of the pen down to the lime chip layer, and elevated the other side a foot or more. This had to take hours.
I watched one gilt tear bedding off a bale with her mouth and carry it to her nest. All of them do it to some extent. Below is another picture showing a litter in an elevated nest.