Agon before Great Temple

Any%

In this category, you will be coming back from the Early Power Bomb sequence break.
After collecting the Power Bomb, walk along the bottom of Temple Assembly Site's box until you to the right of the door connected to Collapsed Tunnel.
When you are ready to jump, jump straight up, then Space Jump to the left so you get stuck on the side of the door. Then, Bomb Jump up to the top of the door.
Jump off while making sure to go far enough back so that you land outside of Temple Assembly Site's box. Then, make sure you hit the load trigger in the tunnel while walking, otherwise you can't do the next transition. You will know you hit the trigger when the background turns black. Try to walk along the Morph Ball tunnel to find the trigger.
Then, Aether Jump to the top of door connected to Industrial Site, and transition it to that room. From here, jump off back-left or do a forwards-bent Scan Dash off the door to get in the Aether.
Shoot to the door connected to Agon Transport Access as you're walking over, get close to the door and immediately move back. This will force load the room and have it load around you.
After this, just go back and touch the door and you're free to go to Agon.

In this category, you will just go straight to Agon after Item Loss Skip.
Just walk along the bottom of Industrial Site's Aether box over to the door connected to Agon Transport Access.
Then, mash B to get a jump and go left to enter the Aether. Once high enough, shoot the door, approach it, and immediately walk back to force load the room and have it load around you (same as Any%).
You can save time by shooting the door prior to getting a jump, but it's a bit riskier.