Cut the fabric. For a 17″ pillow you need a piece of fabric 17X38 inches big. For other sized pillows you need the fabric to be the size of the pillow side (in my case 17″) by the side times 2 plus 4 more inches. So for mine it was 17″ by (17X2)+4

Finish the short edges of the fabric.

Fold one side under and hem. This is for the side of the fabric that will show on the outside.

Fold the fabric in on both ends (right side of the fabric inside) so that there is a square the size of the pillow in the middle. For mine this means that I folded each end in 10.5″. There should be a couple of inches of overlap. Iron or pin in place.

Sew across the top and bottom.

Flip inside out and stuff the pillow into the pillow case.