1. First trace your foot on the paper sheet. Cut out the shape neatly then trace the pattern onto your pieces of felt. Trace the pattern twice per piece of felt, as we'll need two pieces per slipper- one for the sole and one for the midsole. When you're done you'll have 4 foot-shaped pieces of felt: Now place the foot pattern onto the sweater with the heel 1 1/4 - 1 1/2" away from the bottom edge of the sweater. Draw an arc around the pattern that is 1" above the toes and then extends straight down.
2. Cutout Flip the pattern over and repeat steps for the other foot. Use double sided tape to stick the felt piece onto the sweater. Then repeat on the back side. Take your time to try to lineup the two pieces of felt as precisely as possible. Now sew with good side with facing up and stitch all around. I'd suggest using a contrast color embroidery thread, so that it will become part of the design.
3. Now cut off each of the sleeves 5" from the bottom. Stitch the sleeve opening shut. Round the other end. When you've finished this, the plug will look like an egg with a flattened bottom. Now you have all the pieces and are ready to assemble the slipper! Place the the plug over top of the foot bed with good sides together. The pointed area of the plug should be lined up with the center top of the foot bed. Tack stitch together at the point. Pull the plug back 1" and tack stitch the left and right corners onto that place. Make two more tack stitches.
4. One at the midpoint between the point and corners stitches on the right and then on the left. Starting from the left side, moving right, stitch all around, evenly distributing the excess material from the foot bed as you go. Flip right side out, and then make two snips on either side of the heel that go almost all the way to the felt. Fold the two side pieces to form the back of the slipper. Insert the center flap into the slit at the bottom. Close the back by running two rows of stitches up the back about an inch apart. Then sew straight across the bottom to close the slit.
5. The last step in finishing the slipper is to add a collar. This will give the edges a clean finished look and keep the slipper from being so floppy. Cut all around on the bottom of the sweater. Trim to about 2" high and cut in half. Then put a little double stick tape on each piece. Fold in half around the top edge of the slipper and tack stitch a few place to keep it from flipping up. And that's it, they're ready to wear!