Many times this will allow the rug to lay smooth for a while.
How to get rugs to lay flat on carpet.
Apply the tape to the edges of rug.
Double sided tape could be used in place of the carpet tape.
If the ends still curl up move to the next steps.
With the towel still covering the carpeted area hold down the iron and press.
Lay a damp towel over the edges and iron them flat.
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.
Take a wet towel and moisten the areas where the carpet is curling.
Apply carpet tape around the edges of the rug.
Turn over the rug and lay it on the carpet.
Then take an iron and set it to a medium heat.
Turn over the rug with the right side down.