Yeah, you're pretty much doing the Charleston here. Your knees are all over the place. I'm way, way more concerned about the way your knees are knocking in than the slide. Your knees/thighs, should stay over the long axis of your feet. You have to keep your knees driven out and keep them there especially on the way up. It's hard to be sure from this angle (getting footage from the rear 45 degree angle helps), but it looks like your stance is fine.
Get a TUBOW and use it starting with your empty bar warmup. Set it up about 3 cm in front of your toes. When you start the descent, break at the hips and knees at the same time and get bent over (you're pretty good on this compared to the rest of your form). Your knees should touch the TUBOW by the time you are halfway down and they should stay in contact until you are halfway back up. Do not knock over the TUBOW. Film each set and watch it when you're done so you can catch issues.