1. Go to your local fabric store and pick out some fabrics that you like. Remember that the shapes may not capture a large pattern, so look for small patterns that will still look great in small pieces. The fabrics that I used are quilting squares from Jo-Ann Fabrics. They were ideal for just getting a small amount of fabric in a bunch of different patterns.
2. Purchase Heat n' Bond paper which will attach the fabric to the onesie. I used ultra hold, but if you want to sew a boarder around the edges of your shapes, you need to get the "light" version of this paper.
3. Pick out some shapes and draw them on a piece of paper. Cut that shape out so that you can use it at an outline.
4. Iron a piece of the fabric (large enough for the shape that you have selected) onto the Heat n' Bond paper. Follow the directions on the package to make sure you are using the right side first.
5. Trace the outline of your shape onto the back of the Heat n' Bond, then trim the Heat n' Bond and fabric into your shape.
6. Remove the back of the Heat n' Bond paper and place your shape on the onesie.
7. Follow the instructions on the package to iron the shape onto the onesie with the correct amount of time of ironing.
These should be washable, however I have not personally tested that.
These make an adorable personalized gift for a baby on the way!