How to glue stones and shells to burlap-covered wood?
I have been working with all different types of glass on a daily basis for over 20 years, stained, frosted, fused, etc. I create mosaic art pieces using all sorts of different backings. For example: Glass on glass, glass on wood, glass on metal, glass on ceramic, glass on plastic, and the piece I'm working  on now is glass on egg shells. Yes, glass on blown out egg shells.

Over the years  I have tried everything from Elmer's school glue to contact cement, to hot glue guns and I have found that the best adhesive to attach any type of glass to any surface is "Weldbond". It is the strongest, weather and water proof, a little goes a long way, dries clear glue. And best of all it's inexpensive. You can find it in any craft store for around $8.0o. I swear by it, I wont use anything else my glass pieces. I promise you wont be disappointed. Here are a few links, check it out for yourself.

https://www.walmart.com/ip/Weldbond-All-Purpose-Glue/47657022

https://www.amazon.com/Weldbond-8-50160-Universal-Adhesive-5-4/dp/B00P94NRDE/ref=sr_1_3?ie=UTF8&amp;qid=1502264340&amp;sr=8-3&amp;keywords=weldbond+glue+mosaic+adhesive