The pillow cover illustrated (along with my Auggie-Doggie cat) was made from a large basket quilt block. I filled the basket with Yo Yo 'flowers' (with button centers) and placed the block on point to increase its width, surrounding it with corner triangles.
If you're a new quilter you may not have a stash of unused blocks yet. Make the quilt blocks I used on page 3 of this pattern, or sew one or more of the quilt blocks in the block library. You can also search eBay for the term vintage quilt blocks -- an easy way find all sorts of inexpensive quilt blocks for your projects.
If you prefer, use a piece of fabric for the front of the pillow cover, rather than a quilt block.
You can buy pillow forms of all shapes and sizes at discount and craft stores. Try to choose one that's the same size as your finished pillow front or go just a bit smaller for a tight fit. If a quilt block you adore is too small to make a pillow, or if it's an odd size, simply add borders around it to change its dimensions. I sewed together four blocks from a past quilt swap to make my pillow.
Use any backing fabric that coordinates with the front of your throw pillow.
Seam AllowancesI like to use a 1/2" seam allowance if I'm assembling a pillow cover from a quilt block surrounded by a border. The four blocks above already have a 1/4" seam allowance around their outer edges, so that pre-determined my seam width. Use a seam allowance that suits your project.
Quilt the Pillow FrontBack the pillow front with a piece of flannel and quilt as desired. Or, sandwich it with a piece of thin batting and backing and quilt.
If you'd prefer not to quilt the pillow at all, that's okay too. Instead of quilting, I pressed fusible interfacing to the back side of my block unit before continuing. Interfacing adds a bit of depth and helps protect the block's seams when it's time to wash the pillow cover.