ROFL... ergonomic is NOT how I would call most of my drawing(perhaps that's why I have such problems!). In about 80% of the time, I am sitting in my adjustable bed with head raised about 45 degrees and knees/legs about the same with my laptop on my lap... then.. my tablet is sitting SIDEWAYS on my chest to that it's inline with my right arm bent at around a 30 degree angle... yea... I probably looks as funny as it sounds....

Since I have a laptop.. the other 20% of the time, I usually have the laptop close to the edge of the work surface and my tablet to the right and away from the edge a few inches and at about a 10-20 degree angle...