Thank you! This help me fix my issue.
So I had the same issue until I realised that my extra abilities were stuck behind my spells and I simply wasn’t seeing the prompt. Just go into edit mode and move it and walk up and you’ll get the prompt.
I came across the same issue while in the cave. I ended up abandoning the quest " Putting It All Together" and picking it back up since the npc “Sef Iwen” was still standing next to me. I then repeated same steps, applying the wood, silk wrappings, and it finally allowed me to place the Runic Power Core.
FYI - I had to abandon quest & pick up again because after finally putting together the Golem there was not dialogue between the Golem & Sef Iwen.