A while ago I used this tutorial from Cottage Magpie to make this monogrammed pillow for a friend. This is a great, easy to follow tutorial and I love that the pillow has an envelope style back so that you can remove the pillow form and wash the pillow cover if needed (which in my house, is definitely needed). I used simple linen bought at Joann's for this but you could use any fabric. I made the monogram with wonder under and just a little scrap of white cotton fabric. I ironed it on, then sewed around the edges. I did this before I sewed the pillow together (you sew it from three cut pieces). If you are making this with a monogram, be sure to not put the letter right in the corner before it's sewn, leave some room for the seam allowance.
I plan to make another one of these for my daughter's new bedroom!