I struggled with them to start with but its timing of your ollie thats the key..
I got stuck on uneven flow for ages, i got some tips from the forums and find them pretty easy now.. as soon as you ollie bail your board (triangle on ps5) and go straight to eagle spread, then its just a case of find the right glide path by pushing forward or back. Some of the challenges where you have to land in a dumpster truck or a monument/palm trees can be a bit harder as it requires you to slam and fall into the target require a bit of a grind but they are all very acheivable.
Good luck..
