Find the fourth corner. It’s usually the one trying to escape off the edge of the table. Grab it firmly.
Turn that fourth corner inside out and slide it into the pile of its three friends. You now have all four corners nesting inside each other like a very cozy, very confused family.
How to Fold a Fitted Sheet: Full Guide with Pictures
If you’ve done it right, it should look like a sad, elastic-edged rectangle. Don’t panic. That’s progress.