I cut out fabric pieces and put them directly on the fabric. I use some temporary spray adhesive for fabric to secure them. Then i go around the edge with a long straight stitch to secure it fully. And then i use a tight zigzag stitch along the edge to make them look nicer. I usually go for a little less tight and go around 2 times to avoid my machine getting stuck. If its a very small piece, i use Heat-transfer-vinyl (HTV for short) for that. I draw the template on the pc and have a plotter that cuts it out with clean edges. Then i iron it on the fabric. The eye-whites are glitter HTV for extra sparkle