If you visit your local wholesale yard you will see thousands of field grown, B&B stock all machine dug and in wire baskets. The wire helps to protect the ball from the slings, hooks and fork lifts that we use to move the plants around.
What to do if no machine is available and you need to dig a tree? We have to fall back on the time honored method of hand digging. A major part of the value of the finished plant is in the quality of the B&B job. Here is how I hand dig a Hinoki Cypress.
Materials - burlap, spade (I use AM Leonard) file, pinning nails, twine, felcos and calipers.

Tie up the branches, this protects the tree while digging and also while in transport.

Shave soil off the top until you reach roots. Define the size of the root ball, you can consult American Standard for Nursery Stock for root ball sizes.

Dig down forming the ball as you go, cut roots with the sharp spade, use mattock if you find stones.

Pin on burlap.

Pin on top ring of twine, I usually double the twine for this.

Make bottom ring, them go up and down all around the root ball.

Remove nails in top ring and lace it up as shown to form the star. Ball will tighten up with this step.

Break loose the ball at the bottom by tilting, if roots are coming out of the bottom they will have to be cut. Don't try to lift the ball. Throw soil under the root ball as you tilt from side to side and the ball will rise to the surface, then roll it out.

Patch up the bottom with burlap and lace it up, cinch it up good and tight. Move with ball cart or loader.