I would very strongly counsel against going anywhere near chain link fence for any learner.
Firstly it can cause serious hand injuries when the rider falls with their fingers stuck in the wire. Secondly, it teaches clinging rather than riding and can lead to a twisted riding technique.
My teaching method is to have the learner sit on the uni while holding a suitable rail and move the pedals around a bit to get the feel while controlling the rolling direction (sideways control rather than the obvious fore and aft). This teaches the basics of steering which is vital to staying upright.
Just do this for maybe fifteen minutes but it depends on how they progress.
Then move to block mounts. A portable aerobics step works really well and are easily found in garage sales and junk shops. The blocking stops the wheel rolling back and elevates the rider prior to the mount making mounting easier. Put pressure on the back pedal to hold the wheel against the block then step up with the other foot to the front pedal.
Start out this stage on grass (as smooth as you can find) with a very small downward slope. The slope helps them to get moving while the grass allays the fear of dismounts and falls. Learning to fall should be a parallel process of advancement as riding skills progress. Then move to a smooth hard surface which will then seem really easy.
Get them to concentrate on one aspect of riding at a time. Hit the front pedal squarely, stay upright, go straight, get past the first half turn. Eventually they will be able to combine these skills and they will be riding albeit rather wildly.
Demonstrate how the uni leans back while the body leans forward to maintain the contact point under the centre of mass. Explain how the starting lean is much more than expected to get the body mass moving quickly and how the uni is driven rapidly into the position under the rider.
I found these suggestion helpful for learners.
Riding is a continuous fall saved by intervention of the wheel, just as is walking is saved by the step…
Steer the uni in the falling direction by pushing the nose with the inside of the thigh. The wheel should basically be where you would have put your foot if walking.
Later they can learn to tilt the uni to steer by leaning the body in the opposite direction from the turn.
Don’t worry about weight on the seat at first. Beginners usually “walk on the pedals”. Weight on the seat requires a more advanced control of the angle of uni, which will shoot out from under a learner if they try it too early.
Have the seat comfortably high so they can grip it between the upper thighs while standing on the pedals with their legs somewhat bent.