You want a fairly uniform surface and material under the fabric/netting material, as free from organic material as possible, place the fabric, then some of them are made to basically create pockets of gravel, others, you just spread whatever locally used road base on top of.
Basically, you don't want plastic (gumbo clay/fat clay) or organics below the road bed. Either will pump when wet, but with organics, you also are dealing with long term deterioration of the material, that also leads to settlement. This goes for any type of roadway. Water makes everything worse.
In principle, to create a good road bed, you first cut the ditches, rolling good material up on to the road bed, then box it out, and place your base. So, by default that creates a road bed approx 6"-12" higher then the virgin ground was, and also gives an area to contain/channel water. If the subgrade (soil below your base material) is suspect, and the ditch/scale Hold water, that is also a problem, as the water will get to the subgrade from the side ditch, and cause problems over the coming years.