Pillow cover to crochet, on the diagonal

 Pillow cover to crochet – on the diagonal
Materials:  2 balls (100 grams) worsted weight yarn.  Size G/4mm hook
Yarn needle
Bobbin (optional)
a pillow to cover, about 15 inches wide

The fabric should be a tight-ish gauge because it is a pillow cover, and I don't want the fabric underneath to be part of the visual effect.  Also, the pattern stitch has lots of chain stitches in it, so in a looser gauge it is a bit lacy.

Pattern stitch:  
Increase row:  ch1, turn.  (Sc1, ch2, sc1, ch2, sc1) in next ch2 space.  *(sc1, ch2, sc1) all in next ch2 space.  Repeat from * to end of row.
Decrease row: first decrease row:  ch2, turn.  Sc1 in next ch2 space.  *(sc1, ch2, sc1) all in next ch2 space.  Repeat from * to end  of row.
For additional decrease rows:  work as first decrease row.  At the end of the decrease row, sc1 in sc1 at beginning of previous dec row.  The last row will just be:  ch2, turn, sc in sc.

To start:
Row 1:  Ch2.  (sc1, ch2, sc1) in 2nd ch from hook.
Work Increase Rows until end of first ball of yarn.  When there isn’t enough yarn to finish another row, stop at the end of the last row where there was enough yarn to finish the row.  Do not cut the yarn that is left over – wind it onto a bobbin to keep it out of the way, if desired.
Other side - does not look diagonal
Join the next ball of yarn at the beginning of that row and continue with Decrease Rows until 1sc remains.  Knot the yarn, but do not cut it.

Lay the square flat.  Fold in the 4 corners to meet in the middle. That is the shape you will end up with.  Starting in the middle with the leftover yarn (possibly on a bobbin), thread the yarn needle, and use the yarn to sew a seam from the middle point to one corner.  Fasten and cut the yarn at the corner, tucking the loose end to the inside of the cover.  *Returning to the middle, thread the yarn needle with enough yarn to sew a seam to the next corner, and sew that seam, fastening off as before. ** Insert pillow form and repeat from * to ** for the remaining seams to finish.