Valences are fun to make.
I like using a "tube method". I just measure the length I want, double it and and in seam allowance. After hemming the sides, I sew the ends together, turn it right side out, then measure how wide the curtain rod is, add 1/2inch and sew a seam across. Put the curtain up, then I use those plastic grocery bags that seem to multiply, wad them up and stuff them in the bottom part. Makes it nice and puffy and does not add much weight to it.