This is what I drive. It’s called decking. This specifically is a new truck deck.
As far as your question, it’s usually an overhead hoist, sometimes manual sometimes electric that lifts the decked trucks off the truck underneath. Sometimes if the dealership or receiver doesn’t have a hoist, a wrecker will be used. It’s against policy to use forklifts. I’m not saying it’s never done, I’m just saying it’s against policy.

The decked trucks steer axle is bolted into a saddle that is bolted to the frame or locked and bolted into the fifth wheel. Start at the #3 position and work your way forward. A small 3-way like this will take about 2.5-3 hours to get on the ground and ready to deliver.