1. Hold sheet vertically, one corner in each hand.
2. Fold in half by bringing corners together with rounded, elasticized seam on the inside.
3. Repeat from the opposite direction (bottom to top), so all four corners are joined and sheet is quartered.
4. Lay flat and fold into thirds: Start by moving the rounded-edges side into the middle, then layering the other side on top.
5. Flip over and pile with matching flat sheet and cases.