Filling a cavity.

I have a very nice awaseto that I want to glue to an Iroko base but before I do that I want to fill the cavity on the bottom so water doesn't collect in it. What would you recommend for this?

 

Sugru might do: https://sugru.com/

 

I decided to fill the cavity with Sikaflex 290 DC, this is what we use for Teak deck seams. When I reach the cavity in a couple of years I can very easily remove some of the caulk with a knife and keep on sharpening.

 

We use a Sikaflex product, their self leveling seam filler for cracks in masonry, seams between sidewalk and building slabs, etc. Designed to stick to rocks and cement. Need to build a dam to hold it while it hardens though.

https://www.amazon.com/SIKA-CORPORA...elf+leveling&qid=1566314725&s=gateway&sr=8-25