I got a pjoning hook (that’s the traditional flat hook with angled sides) from Lacis for doing slip stitch crochet.
I really like it! It slips into the stitches really easily, and while I was worried about getting correct gauge because of the angled sides, it turns out that the angled sides are there to help with correct gauge!
At least, that’s my hypothesis.
Gauge is established with the foundation chain; I admit, I used a regular crochet hook for that part because I was worried about evenness.
With slip stitches, the size of the last loop you made is determined by where the angled hook sits in the stitch from the previous row, except that I want the loop to be a little bigger because it’s also going to hold the next stitch I make and so I need a little slack. Having the loop of the next stitch formed below that on the hook means that it will be just that little bit larger.
There’s a sneaky thing about knitting stitches that many people don’t realize, and I think it holds true for slip stitch crochet as well (probably fiber arts in general, now that I consider the matter): the size of the stitch I just made is partially determined by how I pull on the yarn as I make a new stitch. I think it might actually be more important in crochet than in knitting because there’s no needle sitting in the stitch until the end of the row to keep it from shrinking too far.
So, after I make a new stitch, there’s a loop on the hook, right? It could end up being any size depending on what I do next.
I insert the hook into the next stitch from the previous round until the stitch is tight around the hook. You see how the loop on the hook is underneath?
Then I pull gently on the yarn as I make the next loop on the hook so that the loop already on the hook is snug but not tight. This will keep my gauge the same. Or it will once I’ve practiced enough that I pull the yarn consistently after each stitch. But it’s pretty clear to me that consistent tension will lead to consistent gauge because of the angled sides of the hook.