How to improve contact between non-flat pan and stovetop
I have one of those pans, and I also have a glass top electric stove, and the answer is that you can't use the pan on the stove.  Not only does it not make good contact, an electric stove is incapable of the rapid temperature changes you need for proper paella, particularly the blast of heat at the end to make the proper socarrat (brown crust).
I recommend that you instead get a portable butane stove, like the one I use, and use that for your paella-making.