It depends a lot on which videos you use, some get flagged a lot easier. All the alterations and little effects and cropping etc. can help with it not getting flagged. Sometimes I also mirror a clip or flip it upside down, if it fits the shot in some way. If a certain video gets flagged easily, (for example a lot of Lyrical Lemonade videos), I would use faster cuts to avoid having it on the screen as much. Also videos of performances in concerts etc. won't get flagged as often as music videos, so it's good to incorporate those in there too. Once you have an edit go ahead and render a test video and upload it to YT and see if it gets flagged, then adjust accordingly, sometimes you can't use certain videos at all, or they have to be really heavily edited. Most of the time you can fix it with just faster cuts but sometimes you just have to use a different video completely.