Of course it's the most obvious makeshift but you need pins to hold it. If you want I can tell you how best to fold it. The width of the towel must be enough to go around your waist at least three quarters.
Note that the type of material the towel is made of can effect how absorbent the makeshift diaper is. Some material combinations are better than others. Regardless, all makeshift towel diapers will need plastic pants (unless you are going for the 'I peed' like )
I do this all the time for my plushies with washcloths, I even have pink and blue colored washcloths and pins so that my boy and girl plushies are more cute. For an actual diaper though you just need to fold the sides over each other and pull the corners out.
I used towels for many years before I could afford to buy disposable nappies or was given them by the NHS for my bedwetting. My mum started using old towels on me when I got too big to make the use of cloth baby nappies practical. I had the idea too of holding them in place by using stretchy knickers (e.g. Playtex), which removed the need for pins. This served me well for many years until I started wearing disposables.
I still have some old towels and stretch knickers which I sometimes wear when I want a change from disposables simply for the pleasure of a cloth nappy and plastic pants.
I'm actually trying this right now. After trying a towel, I knew it wasn't going to be enough to satisfy the urge for a diaper. So I added a flannel sheet folded many times into it. While the tie on the end isn't great, it matches the explanations given by many ABDL stories. I cannot put my legs together.