This level is done in the Secretless and 100% categories.
In Secretless Edit
...I don't actually know the route. Sorry.
In 100% Edit
If doing an IL, enter the level on challenge mode.
Progress through the level normally until you get to the area with two Blockhoppers. Stand on the second one and wait for it to jump, then jump off to get the star coin. A precise triple jump off both Blockhoppers can reach the star coin faster. However, this is too inconsistent to be done in actual runs.
Again, progress normally through the level until the area after the check point. Here, immediately hit the 2nd block to make a P-switch appear, then jump up off the Blockhopper right behind you and hit the switch. Go back on the platforms that appear.
After you get the 2nd star coin, go forward on the platforms, jumping off the last one to avoid falling into a pit. Kill the Boomerang Bro. up ahead with a fireball, and fall into the sand next to it. Use the sand to access a hidden area under the last area of the level.
Jump onto the Blockhopper under the level. This enemy can be controlled by facing the way you want it to go. Position it under the last star coin, and jump after it does to get the coin. Go back up to complete the level.
Position the wall to the right of the star coin a couple pixels from the edge of the screen. Get the star coin and you should be ejected into the wall. Duck-jump up to the flagpole.