No sewing, just cut and tie.
I made this sling to carry my 9 month old boy on my hip.
I don't recommend this sling for any other ways of carrying, because I'm not sure the fabric will hold; so please be careful.
Step 1: Cut the shirt
Don't pick something too old or torn.
Cut the shirt from armpit to armpit, as shown in the picture.
The sling is the bottom part, the rest goes to recycling.