if you're opposed to using dog holes, here is a bit that can be used to drill a hole to hold your glue bottle upside down as someone else suggested.
https://smile.amazon.com/Vastar-Tit...21&sr=8-1-spons&keywords=step+drill+bit&psc=1
:gar-Bi
https://smile.amazon.com/Vastar-Tit...21&sr=8-1-spons&keywords=step+drill+bit&psc=1
:gar-Bi