Since it is Christmas I’m doing a Christmas inspired one, you can use any shape or object you want. Just look on google and you can find a ton of inspirations. The concept is the same for the construction :)
I forgot to take pictures of the process but it is not very hard so I will explain in simple detail.
Step one: Find a shirt or onesie that needs some attention to it. and find the basic pattern you want. For Christmas you can make a tree, present, snowman, if you are crazy and really good make a manger.
Step two: Get some scrap fabric to match with your pattern, and some interfacing (if you don't have this on hand don't worry about it, it is not necessary. I of course got some green scraps, and found randomly in my scrap container these long strips of blue and red. It was meant to be :) I also used some fabric paint I had so I didn’t have to sew the little dots on.
Step three: cut out the shape of your pattern. The tree was easy, the green tree, the little truck and some red and blue for tinsel decoration. If say you were doing a snowman you would need some white, or off white color, something for a scarf, maybe a hat, the rest I would do with the fabric paint.
Step four: Sewing. (This is were you can iron your interfacing to the WRONG side of the fabric tree) First I sewed what went on the tree first. So I sewed the red and blue garland tinsel stuff first. Just one line of sewing so it will fray a little when I wash it. Then you just put the tree on the shirt, pin it in a couple of places. Then sew all the way around the tree. I used about 1/8 seam allowance (the edge of the fabric to the sew line). Then I just added a little dots here and there for small decorations. You can use glitter or sequence I just didn't have any of those things.
Step Five; Try it on your little guy or girl and admire your hard work :)
Here is some other stuff I found online….
