There are 3 beginner strats shown below. All are beginner friendly but have slightly varying levels of difficulty. 1 is the fastest, but is a little more difficult and doesn't have any lag reduction. 2 has a slightly easier movement and camera setup for getting on the island, but is slightly slower. 3 shows a similar strat as 2, but has a different camera set up for some lag reduction which can also be applied to the 1st strat.
You can stay in C down for an easier view, but the C-up does reduce lag significantly.
To the Top of the Fortress is the second mission in Whomp's Fortress. The 2nd star must be selected when entering the stage in order to spawn the tower while not spawning the owl.