Place two 6 x 2in (150 x 50mm) boards cut to the size of the window, front and back. On the back board add a 4 x 2 (100 x 50mm) or another 6 x 2 if depending on the pitch you want. Nail them together with a short 4 x 2 on each end. Next nail on 6 x 2 end pieces flush with the ground. To get the angled piece, just set a 4 x 2 on the ends and draw or snap a line, cut and nail in place.
Next build a 4 x 2 frame for the window to sit in and attach it to the base with hinges. I used salvaged hinges from an old door. They’re made of heavy brass, can be separated easily by removing the door pin (making the cold frame easier to transport in two sections) and they were free.
The slider works well at maintaining the temperature because I can slide it open to control the heat build-up on sunny days. Strawberries are permanent residents with enough room left for tomato, cucumber and other tender starts. When the strawberries bloom I prop the top open to allow germinate in the greenhouse. The germination rate was fantastic compared to what I was used to. Once they were growing well I wheeled them out into the garden. The crop was amazing for such a small area, with plentiful thinnings and then large carrots, often up to eight ounces each, with no sign of carrot fly.