For the hopscotch top and dress, using knits and depending on the knit fabric you are using, the gathers can become a little bulky. I would suggest making sure you use two lines of gathering and if you want to, three just so that you can get the right consistency of gathers. It makes it interesting too with a smaller seam allowance as with woven fabrics Liesl allows 1/2 inch seams. Knits work a little differently and takes a little bit of practise to get the technique the way you want it.
Keep practising on scraps with the gathers so that you can perfect the look you are going for. Knotting the gathering threads are ideal as Nicole has already said, just pull the threads to line up (you can do this for sleeve too) and when the length is right, knot at both ends and fiddle with the gathers to get a nice result. I don’t pull the gathers down as I’m working but I do make sure they are sitting nicely before I get to them and this just means stopping before this point and aligning the fabric so that it is straight down – how it is meant to be.
Hope this helps
Tamara