Yes, hang from the waistline to allow it to drop.
With a full circle skirt part of it will hang in the warp/lengthways direction and that part is unlikely to drop much, if at all. Part will hang in the crossways direction, that might drop a little but probably not much. The rest will hang diagonally/on the bias and those are the areas which will drop most; sometimes several inches on the length of a skirt, and it will drop regardless of how you might have hung the fabric prior to cutting.
There are two bias directions in a length of fabric and it's impossible to hang with both biases vertical at the same time, so sadly yes, you did waste your time, but it did no harm and it's a lesson learned for next time.