Simply lock those pieces down I suggest locking down the triangle part first... putting the Tip (green crystal) behind it sort of if you image it's 4 tiles everything but the tip get placed in the lower right... the tip goes in the upper left... then raise most the pieces 4 or 5 times with the tool... then raise the tip up till it is between the V at the top of the Triangular piece... then place the base under it being sure to secure it... nice thing it works as a container... once you have it all locked in place (honestly don't think anything matters really but the tip.... ) then use the tip at the top to impart the Titan slayer property onto your weapon in your hand... this seems to work several times... so no worries.How do you build that obelisk? Do you just lock the pieces down? Or does it somehow auto-lock in place?
Info: both the grant peace and summon perhelion spells can be re-cast once per day. The key and the candles are not destroyed by casting, the obsidian, pumice and normal regs are.
If you have pictures of the Obelisk that you did with your T-Hunter to get the goods just follow that. It looks pretty well identical when you are done.