I went to Menards and bought two panels of pink insulation: 4'x8'x2". I covered them with flannel sheeting (twin set). They lean against my wall. Except for a windy day with the windows open my blocks stay up nicely for arranging. On windy day I use my yellow-head quilt pins.
I make bed size quilts and sandwich them on the floor. Wouldn't trust anything that big to stay put.