A while back, I wrote about a method to make the bottom loopy edge of long-tail cast-on looser. I haven’t ended up using it much, though I do think there are circumstances where it might be the best option. But a little while afterward, someone taught me a trick: after casting on each stitch, set your right fingertip down on the needle to ensure that there will be plenty of space between each stitch. The further apart the stitches are cast on, the stretchier the cast on will be.
When stitches are close to each other on the needle because of tightness, there’s less yarn between each loop. When they’re cast on with more space between, there’s more slack between each stitch so the row of stitches will pull further apart when stretched.
When I cast on stitches quickly, without paying attention, I pull them up tightly, so they sit next to each other on the needle, sometimes even more closely than in this photo.
Here’s a fingertip sitting on the needle, which I put there before casting on the stitch in progress. This is a help, but the stitches can still get a little too tight if I’m not paying attention.
But the good thing about putting my index finger there is that it helps me remember to not snug that bottom loop up too tightly while casting one, and I get a looser cast-on as a result.