I brought this up before on another thread but it sort of applies here too..........
What about using the piece of carpet just about every car has in the trunk to cover the spare tire as a landing pad? Some of those even have a piece of fiber board attached to them to make them support the weight of the objects in the trunk. They are certainly firm enough to sit on rocky terrain without much flex, and if needed a couple well placed rocks under one or more corners would level it up. Or how about the bed of a pickup truck? Or the hood or roof of a car or truck? Does the landing area have to be flat flat as in zero angle? Maybe the metal of a vehicle is not optimal?
I took 5 pieces of cardboard about 3' x 3' and taped them together. This fits in the back of my 4Runner nice, but it would certainly stand on end in a sedan behind the front seat. It's heavy enough not to blow away and when it gets muddy or damaged I just make another one. I live in the country and don't always cut my grass regularly so I needed something. I could also put this on the hood or roof of my 4Runner if the only place to launch/land was from a creek.
If you are really going remote, and you are way out in the middle of nowhere and everything is being packed in, I am sure you could rig up one of those collapsible/foldable car sun shades (they sell these now as drone landing pads for a lot more money) and with some para cord tie that sucker to some spaced saplings/trees. I get the whole portability thing but if you want to be totally portable, you are going to need to learn to hand catch.
I tried to hand catch a XK X251 brushless racer and only did it once. There is a lot of force at full throttle and it was more surprising than I would have thought. Added to the anxiety and potential disaster. I got lucky.