How To Uncurl MNH Stamps?

Sorry if this has been asked elsewhere, I did check but didn't find an answer that addressed my specific circumstance.

I just got these in the mail and while in the glassine envelope they seemed nice and flat but as soon as I took them out they curled like crazy! They are MNH, the gum is all intact but they seem kind of extra thick and dry?

How do I flatten them out? Do I just press them and hope for the best? Is there some secret trick?
Any advice would be appreciated!

This might help:

https://stampsmarter.org/learning/H...Curling.html

Thank you @poofo!
I followed the directions and they are significantly improved!

The gum you describe is normal for that issue.

The curling could have possibly been due to differences in heat/cold or (more often) humidity like bringing the stamps in from an outside mailbox. If you left it in the glassine with a weight on top they should have flattened out as the paper and gum adjust to current conditions.

Since they are MNH and I assume that you are going to mount them on album pages, I would suggest using a plastic stamp mount which might provide enough stiffness to keep them flat. Of course, being in a closed album might also press them.

Thanks, guys! I need all the advice I can get being so new to all this.

Many of my Russian stamps from the 1930's on are prolific curlers and have never really flattened out.