I use these:
https://www.statelinetack.com/item/...ce^c-plaid^109335747708-sku^489228-adType^PLA
If your ground is uneven, you will get either sagging at bottom or top. As other posters have said, if the charged wires of the fence (any horizontal wire other than the very bottom black one) touch the ground, the fence will be grounded out and will not work well. If you are using a battery powered charger, it will also quickly kill your battery. My ground is VERY uneven, so I use a lot of posts between the actual posts that are integrated to the net.
As for the landscaping fabric, I would not trust it to do the job you intend it to do. The chickens will consider it to be a challenge which must be met: "Must lift that black stuff to see what is under there. Must shred that black stuff. Must see if that black stuff will make a good snack."
Instead of putting something under the electronet to block grass and weeds, I just use the push mower. I move fence line in, mow a strip, move fence line back. Often, depending on where it's set up, it's easier to move the north and west sides in, while moving the south and east sides out. Other people use weed killer. But, I'll not use it b/c it poisons the soil, and glyphosphate is an endocrine disruptor.
I keep ground rod near origin of fence and power supply. If weather is dry, I water the site. Even with clay soil, it takes a lot of water to penetrate deep enough to keep the soil wet.