Adding to the "nutshell", don't forget 1) a good seal around the outer edge of the plastic sheet and 2) a piece of tubing running down to your collection container, so you don't have to remove your plastic to get at the water.
Advanced solar still: make the hole a little larger and put green leafy material around the bottom of the hole. As the sun warms the vegetable matter, the vapors will condense and give a higher water yield. Leave one corner of the plastic loosely secured (use a board vs. lotsa rocks) to change out the green stuff as needed.
Do not pour waste water directly in the bottom of the hole; you can contaminate your container and get sick. Instead, dig small perimeter holes, at least 12" from the edge of your main still hole, to pour the waste water in. The soil will help to filter out contaminates, and while you won't get 100% reclamation, the saturated soil will give a decent yield. Some folks I know put liquid human waste in the "filter holes", but I just don't go there. Maybe Kevin Costner can drink filtered pee, but I will exercise all my other options first, thank you.