It may help to think of this as similar to folding one sock over another. At this point, the elastic from both sides should be lined up neatly together. If you’re left-handed, fold the corner in your left hand over the corner in your right hand instead.
By folding the bottom corners one at a time, you’ll end up with neater creases. If you prefer, you can fold the bottom 2 corners together, then bring them both up and fold them into the first 2.
An easy way to smooth the sheet is to slide your fingers into the fold at the bottom of the sheet, then gently pull and shake the fabric until the edges are lined up.
If the corners do unfold, you may have to shake out the sheet and start over.
When you’re finished, you’ll see an L-shaped fold running along 2 edges of the sheet, with the elastic on the inside of the fold.
If you’re doing this on a mattress or a carpeted floor, you might not get the same sharp creases you would on a hard surface.
All of the folds, corners, and elastic should be completely hidden inside of the sheet.
If you have a king-size bed, you may need to fold the long rectangle into quarters rather than thirds. To do that, just fold the sheet in half lengthwise, then in half again.
