I really like this instructional on yoko tomoe nage from Dominic Bell:
https://www.bilibili.com/video/BV1744y1H7EE/
The way he talks about the rolling under the uke. But most crucially the way he explains the landing, where you need to land "under" the uke. And finally your foot placement. In BJJ when we pull guard, we tend to place the foot on the uke first. But in yoko tomoe nage, the foot placement on the uke goes last.
I also find this one from Justin Flores compliments it: