Scalloped hem fail

I followed this tutorial https://youtu.be/EM2DH6ilS6 or so I thought, and tried it out on shorts I was making and it just turned out awful so I had to cut them off and I made booty shorts. What did I do wrong? I really want to make the peppermint magazine spring shorts with a cute scalloped hem at the bottom.

I'm thinking next time I'll try making the scalloped hem on some fabric and not on the actual garment.. I thought it was gonna be pretty straight forward.