You fold the sweatshirt in half, carefully matching shoulder seams and underarm seams, having the front on the outside. Take your scissors and boldly slice through the center front.
Cut your final fabric choice :>} in a length twice the length of the sweatshirt plus 1-2 inches and three inches wide (or wider if you like a wide binding).
Lay the right side of your fabric strip on the inside of the sweatshirt, with the strip 3/4" from the front edge. Stitch the strip in place using 1/4" seam allowance on the fabric, which will be 1" from the edge of the sweatshirt.
Press under 1/4" seam allowance on the unstitched edge of your fabric. Fold the binding back on itself. Stitch across the top and bottom as shown, just above the top of the sweatshirt, and below the bottom edge.
Turn the binding right side out and press.
Topstitch the binding in place.
Topstitch the outside edge as well.
Put your decision making skills to work once again to choose buttons. :>} I chose the one on the right. Make buttonholes, sew on the buttons, and presto! You have a lovely gift for yourself or someone else. Of course you can add whatever other embellishments strike your fancy. I stitched a small dresden plate design on the back and front of one, but repeated washings pulled the fabric away from the stitching, and it looks pretty bad. I may decide to add pockets to this one. It's for my mom, and she likes a pocket to put her tissue in. :>}
Last year when I was having hot flashes every day, it was awfully nice to be able to rip off my sweatshirt quickly! I have a light gray one and a brown one that I wear a lot in the winter.
I hope you are having a delightful weekend. It is about 33 degrees and raining here, occasionally mixing with snow - perfect weather to stay inside and sew.