When hanging baited 330's,the first thing I do is bundle bait.In the areas I trap,popple(aspen) is one of the beavers preferred foods,so this is what I use.Your area may be different,so use what your beavers are feeding on.
I like to use the smaller ,or end branches of the popple,many will have buds on them.I cut them into 5"to6" pieces,and make a bundle about the size of a quarter,or a little bit larger.Each bundle is then wired together about 1 1/2 inches from each end(using light wire,decoy cord would also work).You may also want to scrape a bit of the bark off of a small area,thus adding a bit more eye appeal(The removal of a bit of bark,really shows up under the dark water).
The next step is to bend the trigger wires.I pull the trigger ends to within an inch of each other,and bend the ends to form a j.The bait bundle is then slid onto the trigger wires.(push the bundle up a ways,do not leave it right on the end.
I have taken a half dozen beaver from one trap, and not had to replace the bait.Though I like to have extra bait bundles with me.
The next step is to wire or cable your 330.If you use wire,use a heavy gauge .To be on the safe side,you may want to double your wire.Cable is stronger and may also be used,try 3/32" cable.If you use cable make sure to have adjustable end loops on the end that will be above the ice.
Your cable or wire is then attached to the spring eyes of your trap.Length of your attachments will depend on how thick your ice is,so you may want make them longer,so you can adjust them when setting.
I like to hang my baited traps,right off of the feed beds.Do not run your traps parallel to the feedbed,turn them so they are perpendicular to the feed bed.
You can vary your depths,but I like to have them fairly close to the bottom of the ice.One thing to consider,leave enough space between you trap and the bottom of the ice.You do not want any catch to come into contact with the ice.A beaver frozen to the underside of the ice ,will mean a lot more work for you.
On the top side of the ice,I place a pole several inches thick over the hole I have chopped.You can also use 2x 4s if you wish,just make sure that anything you use is strong and extends at least a foot past each side of your hole.Attach your wire or cable to your topside pole and lower your trap under the ice.You can wind the excess wire or cable around the top pole to set at the depth you want.
There are several ways to use bait under ice,this is one of the easiest ways I have found for me.