Recoil lugs need to have a slight taper to their sides so they'll easily come out of the epoxy bedding as well as provide good contact to reduce receiver twisting from barrel torque while the bullet's going down the barrel. Decades ago, when Rem. 700 round receivers were tried for magnums used in long range matches, they twisted loose to easy from epoxy bedding from barrel torque. Folks tried 1 to 2 inch long recoil lugs to stop that, but they didn't work. Gluing the receiver in a flat side/bottom sleeve fixed that problem. High power competitors borrowed this idea from benchresters doing the same thing for their 22 and 24 caliber cartridges having much less torque from the barrel.
The lug also needs clearance on its bottom so when the receiver's screwed into the stock, full contact on the receiver around the lug will be made and the lug's bottom won't stop against the epoxy below it.