At Home Depot, I purchased several packages of 6 foot bamboo poles. I took these poles and pushed them into the ground at the base of the bean seedlings, spacing them about 6 inches apart, 8 inches deep. I did this for the along the entire 6 foot row of beans plants.
Next, I wove the first cross pole between the upright poles. In front, behind, in front, behind, etc., until the pole was woven from one end of the row to the other. Gently, I worked the cross bar down until it was in position, about 7 inches from the ground. The next crossbar was woven in the opposite way: behind, in front, behind, in front, etc. . When this one stretched across the row, I gently worked it downward until it was about 5 inches above the previous crossbeam. Continue repeating this process until you have worked up to the top of the trellis. The process of weaving the bamboo poles strengthens the entire structure and the tension holds the poles in place.
Once it is completed, tie off the top two outside joints and the two bottom joints with sturdy twine or braided cord.
As the bean plants grown, they will climb the trellis. The slots between the vertical poles and crossbars provide you ample room to slide your hands between and pluck beans off the vines. If you create a trellis like this, be aware that you may need to tie it to a fence or some other structure near the top if it is not in an area sheltered from the wind.