How to line a baby ball

I would lay out the material, lay each crocheted piece out on top of the material, and cut the material out plus a seam allowance. I would then zig-zag the edges of the material and either sew it together seam by seam or sew the material to the crocheted pieces and then assemble the ball by crocheting the pieces together. If you do the latter, you will have to sew pretty close to the edge of your crocheted piece. I hope this helps. I used to crochet teddy bears. I found that if I used a bulky yarn, a small crochet hook, and tightly single crocheted the pieces, it was very hard for little fingers to get to the stuffing.