Continuing along with this costume. To make Elsa’s undershirt, I continued using Very Sophisticated Pattern Making Technology.
Aka, I took a regular long sleeve shirt, put tulle on top of it, and cut it out to match the shirt.
Tulle is folded in half, so I end up with the full front piece
Repeat for the back and sleeves. Sew together.
Pinning tulle is a bit of an exercise in futility.
This stuff also sheds glitter everywhere. I am going to be glittery for the next week.
Avant Garbe 
I hope all the people at work will notice that your frozen costume is better than all the other frozen girls,,…
I hope so! I have 1-2 sewing friends at work who I can at least count on to notice.