I bought a kit with the bosal foam in it and had the same question. I called the company and asked which side had the glue on it. They didn't know. The girl who answered the phone didn't know and said she would ask someone else and call me back. The end result is no one knew. I just decided to guess, neither side seemed "bumpy" to me. Turned out alright, but I didn't like it when I was done, so I don't think I will ever make another (especially with bosal foam).
Sue