Cut tape to fit each edge of the rug.
How to get an area rug to lay flat on carpet.
Apply carpet tape around the edges of the rug.
The tape is double sided so after you have it positioned where you want you simply peel off the paper that is protecting the sticky side that will be against your carpet.
Then take an iron and set it to a medium heat.
If the ends still curl up move to the next steps.
Turn over the rug with the right side down.
I flipped the rug back over pressed it over the carpet and it seriously worked like magic.
This should flatten the areas out.
Apply the tape to the edges of rug.
Double sided tape could be used in place of the carpet tape.
If possible help hold the area rug in place by setting heavy furniture on top of it.
With the towel still covering the carpeted area hold down the iron and press.
Turn over the rug and lay it on the carpet.
Many times this will allow the rug to lay smooth for a while.