An epiphany struck me. Remember I bought a bag or assorted buttons for really cheap? Some of them have defects on them. I'm really glad I didn't throw them out because they proved to be useful in this case.
I glued the button to the base and then glued the accent onto the top of it. I used PVA glue, which less messy and just as firm as UHU glue.
Ta-da! There you have it. A 3D/pop out accent. You no longer need to run out to buy sponges or styrofoam. Plus, we're saving the environment by using these defective/unwanted buttons!
Do share any crafty tricks that you have!