How to flatten a rug?

A couple months ago, I ordered a sisal rug for my kitchen area. It was shipped to me, wrapped around a cylindrical tube. I’ve had the rug unfurled on the floor for a while and it still has ridges and valleys from being rolled up during shipping.

I was kind of hoping gravity would flatten it out over time, but I’m growing impatient. I’ve tried putting heavy objects on it. I’ve tried rolling it inside out. Anyone know how to flatten a fiber rug?