Greenhouse propagation areas don't need to be sophisticated to be successful.
Simple structures can work great, as long there is excellent attention to detail and timing.
The key lies in balancing light, temperature, and humidity levels and knowing when to make adjustments.
Cuttings that have yet to root don't need much light or water, just high humidity during the first few days. By day four or five, humidity levels can drop as you prepare the plants to callus and begin growing roots.
In rudimentary structures, these changes aren't made through adjustments on a climate control computer; they're done by hand. Increasing shade and applying mist are dependent on both the state of the plant and the weather conditions outside.
Astute growers are on site during the entire growing day in order to make changes as needed. This method requires more labor, but when done correctly, a simple piece of plastic and some PVC hoops are all that's needed to turn unrooted cuttings into healthy young plants.