I just use carpenter's glue and rattle can polyurethane unless it is going to get a lot of exposure to moisture.
In that case, I still use the carpenter's glue but, I use Helmsman spar urethane. This urethane, however, will
amber over time and change the color of your oak.
woodduck had a good idea with screws from the back but, I have never found that necessary. The carpenter's
glue will have an extremely strong bond.
God Bless! Spirithorse