This afternoon I pieced the sun and the sky of my current beach scene. It's all done as a single foundation-pieced section, with the sun pieced first, then the large sections of sky added afterwards. I drew out the sun on an A3 piece of paper and photocopied it before taping it in place to my full size pattern. I cut up the photocopy to use as templates for cutting the fabrics - I just have to remember to add the seam allowance as I go. But I have a different, no-waste method for the cutting the large pieces of sky.
Once I've selected my sky fabrics, I start by lying my marked sky foundation over the first sky fabric, so that there is enough for a generous 3/8 - 1/2in seam allowance all around, but otherwise at the edge of my fabric to minimise waste. I'll place a few pins inside the shape I'm going to cut, but nowhere else.
If there are curved edges to cut, I use an air-erasable fabric marker, and mark right on the lines - you need to go back and forth a few times to make the ink go through, but it's not hard. I just mark a dotted line:
It shows well enough, especially on pale sky fabrics, and will fade on its own:
Then I fold back the foundation and use scissors or a small rotary cutter to cut a generous seam allowance.
For the straight seams, I place my long ruler between the foundation and the sky fabric, again, leaving a generous seam allowance outside the marked sewing line. And again, I gently.fold back the foundation, and use a rotary cutter along the ruler:
And it's done:
When I sew it, it actually goes on top of the foundation, but I forgot to take a photo of the completed sky.