Many times this will allow the rug to lay smooth for a while.
How to get rugs to lay flat on carpet.
With the towel still covering the carpeted area hold down the iron and press.
Then take an iron and set it to a medium heat.
However for rugs that are nowhere near furniture in the center of a hallway or foyer for example the carpet to carpet non slip pad is your best option for preventing ripples in your area rug.
This should flatten the areas out.
Take a wet towel and moisten the areas where the carpet is curling.
If the ends still curl up move to the next steps.
Apply carpet tape around the edges of the rug.
Double sided tape could be used in place of the carpet tape.
Turn over the rug with the right side down.
Cut tape to fit each edge of the rug.
Turn over the rug and lay it on the carpet.