A gangion setup for halibut fishing offers two baits, two hooks and gives you a chance for a double hookup. Also, with two baits the gangion setup will put twice as much scent into the water.
You can use tuna cord or heavy monofilament for your gangion rig. Shown below is a monofilament gangion.
Start with about 28 inches of 150lb+ mono. Add a crimp right in the middle. This will allow the lower corkscrew swivel to pass all the way to the bottom near the lead, but will stop the top swivel/bead half way down. This will allow for separation of the bait/hooks. Next you will want to crimp add a bead and crimp the lower corkscrew swivel. This will be where you lead goes. The bead just above the crimp will be a stop for the lower swivel. For the top corkscrew swivel, add a bead that will stop at the middle crimp, add your upper corkscrew swivel, then crimp the upper barrel swivel.