Once these join up, they zip right along. I’m not sure why I knit faster in the round, but somehow I really really do.
This brings up a handy opportunity to be obnoxiously preachy (what fun, I’m sure you’re thrilled!). Lots of folks get a different gauge when they knit in the round than when they knit flat. The only way to know for sure if you do is…you guessed it…to swatch. Swatch both in the round and flat. Which I know is not what you want to hear. But on projects like this where you knit both flat and in the round, it’s safest to double check.
Once you know if you do, you can switch needles if you need to. For me, my knitting is a tiny bit tighter in the round than flat. It’s not usually enough to make me switch needles, but if it were something with a lot of stitches and pretty tight size tolerance, like say a sweater, I probably would. For the slippers I’m not, but it’s better to know than to be surprised!