How do I get a fold/crease out of a car floor mat?

My passenger side (front) car mart has a strong crease.

Over the past 14 months I have tried a variety of things :

• Leave it flat out in the sun.
• Placed it flat out in the sun with three bricks on it. At the ends and on the crease.
• Just stood on the crease for some time.

I clearly don’t understand how I can get rid of this crease.
What can I do to flatten this mat out? Its the OEM camry mat, if it matters.