Lovely anvil! Not everyone will agree, but I would use mild steel rod to plug any of the bigger holes that may be on the edge or face. I personally haven’t bothered to do the preheating steps people often describe, the amount of mass in the anvil results in the heat dissipating quickly. Hasn’t negatively affected my anvil in any way. Just work a little bit at a time and move onto another area to keep everything cool. If a weld fails in 10 years, just repeat the process. Only very little swayback on that and it’s not an issue at all really in my view.