Several years ago, I discovered that gluing two paper roses back-to-back was a super easy method of creating kissing balls, often used in wedding décor.
If you are using the mat, roll the center of all six pieces. If you are not using the mat, just make sure to bend the petals up when we get to the assembly.
To start assembly, first, add glue to the bottom of one petal layer and gluing it on top another. Make sure to alternate the bottom petals with the top layer.