HOW TO: It is pretty basic really! You can use a fusible web, an interfacing at most fabric stores (directions are on it) or freezer paper and applique glue. Stitching depends on the look you want, straight or zig-zag. If you want little or no fray, you can turn your edges in and/or use a zig-zag right on the edge of the design and shirt. For the twin tree onsies I wanted a lot of fray so I used freezer paper to get the perfect circle, glue to keep in place (NEVER pins, ugh!) and stitched a straight line about 1/4-1/2 inch in, snipped around the edges and washed!
For designs, I usually get ideas from my favorite stores and sketch them myself. The skull and bones were from my sons sippy cup!
The blankets seen with two are so simple, the size doesn't matter it can be a burp cloth to a blanket, and you throw ribbons of all shapes and sizes around the outside for the wee one to fiddle with, and it's a perfect gift!