How do I make corners of my pillow shams full?

Hi Joyce. I'm Cindy. Put extra batting in the corners. You can stuff the batting using a pencil to get into corners.

Use a bigger pillow!

I'm not too sure I understand your question. Are you making a sham for a bed pillow or a decorative pillow. What shape is the pillow? If you use welting or fringe that serves as a nice way to "Pull" the edging out. Another way to make an edging neat, if it is just the fabric with no additional edging would be to use a needle and thread to pull the seam up and then baste around the edging, ironing and then remove the basting thread. The pillows on the right have self covered welting, which makes the edges neat. The pillow on the left has no edging or trim. But I probably used a skewer or knitting needle to "poke" the corners out.

Make sure you're using a large enough pillow to fit the sham. Using a foam pillow helps fill out the whole sham.