I won't go into a lengthy introduction here. This tutorial has a very specific audience. I get that. But, I know there's a need for this out there. When I was looking to make one for the birth ball I carry to births, I could only find pictures of covers or very simplistic instructions (ex, "1 yard of fabric to make a birth ball cover", with no details beyond that.) I bought myself some super cheap, and highly discounted, fabric to play around with and here's what I came up with.
Sewing Machine or needle and thread
1 yard of stretchy fabric (I used jersey knit)
elastic cut to a little less than the circumference of your ball (the width of the elastic itself is determined to your preference. I did one cover with 1/4" and one with 1/8" elastic)
1. Wash and dry your fabric
2. Fold your fabric horizontally, like a hamburger (versus a hot dog Not sure where I got those analogies) with the right sides of the fabric facing each other.
3. Sew each of the sides shut with a straight stitch.
4. If you desire, go back over each seam and do a quick zig zag stitch.
5. You now have a large "pillow case". It should look like the picture below.
6. Take your elastic and use it to measure around the widest part of your ball. Really stretch it here. It just barely has to fit over this part of the ball for the cover.
7. Create a casing for your elastic. Fold the fabric 3/4", so the wrong sides are facing each other (the cover is still inside out at this point) and sew all the way around, making sure to leave a small section open to insert your safety pin and elastic. (If you're using anything but a jersey knit fabric, you may have to fold over a 1/4" first, then fold over 1/2" to create a clean edge then sew your casing. Jersey knit doesn't fray.)
8. Insert your elastic (not pictured). I take a safety pin, attach it to my elastic, and thread it through the tube I created. When its all the way in, sew the elastic together, snip any left over threads, and stitch the opening closed.
9. Turn your cover right side out and shimmy it over the ball. It should look like this:
See why we wanted the elastic tight?
10. With the elastic part of the cover on the floor, find your side seams. Pick them up at the "corners". (Sorry about the blurry. Its hard to get a birth ball to hang perfectly still.)
11. Overlap the corners, pin, and sew on both sides of the pin.
12. You're done! Hurrah!