The scarf joints are glued with epoxy. First the edges are coated in unthickended epoxy, then allowed to draw a little bit. If the wood is absorbing a lot of epoxy, you add a bit more to ensure its saturated. Then you let it dry a little until it gets tacky (though we didn’t wait quite that long), and then you apply epoxy thickened with colloidal sillica and a little bit of cotton, to ensure a strong bond. These scarf joints came out pretty well!