For the boards on top of the houses you just need to find a way to jump up there. Once you find the board, set it as a waypoint to have a little marker directly above it, that really helps when lining up the blind jumps. Then it’s just a case of using the rewind until you get your speed right to hit it. I find trophy trucks are great for the difficult to reach ones because they jump fairly predictably and can smooth out the run up to the takeoff, making it easier to make small adjustments with each attempt.