I use a low folding beach chair that I think my wife got at a CVS or Walgreens store (US). Sorry I don't have a model number or better photo of the whole chair. One "c" clamp is enough to hold a board in place for the laptop. I'm about 61.5 kilos / 177 cm. In a shady spot I can work comfortably for a few hours with short breaks. The low height means I can put my legs out in front of me. The board fits inside the chair when its folded so I can carry them with one hand.
Pics: https://imgur.com/a/1HjaE2W