it looked so much smaller after I glued the excess fabric to the backsides of the rug!
But I get used to it and now I'll show you what I have done. (I made a google search for some information but all I could find was kits and other people asking the very same question or how to make it into a pillow, which is a nice idea as well)
anyway, I started by trimming all excess farbic to about 3 cm width.
Then I folded and pressed this fabric to the inside and glued it to the rug surface. I also made some cuts into the fabric to avoid thick folding lines.
Then I needed to decide wether to first add the silicone to make it slip proof or to secure the edge by sewing on some faric tape.
I went for the silicone first, I thought it will not only make it slip proof but also add some stability to the single knots by "glueing" them.
After this was dry (and it smelled alot!!! so I recommend to do it on a balcony or a backyard. I only had my kitchen and an open window and the result was I felt a little dizzy) I added another layer to the center or rather some single dots.
And the final finish is the fabric tape which I first glued to the edge of the rug (pinning didn't work since the rug was too thick) and sewed into place afterwards.
press the pictures to enlarge them