So, in PvP, you can somehow get out of the FFA arena and build in the overworld by doing the following things:
1.Type /duel (player name);
2.Type /lobby battle;
3.Wait for it to teleport you outside (above the left ocean it seems);
4.Type /lobby leave.
And bam, you are now outside the PvP arena, won’t teleport you back to spawn, able to build. But that should be a Staff only action.
Credits to Augustina for finding this exploit.