Here is a simple guide on how to get the secret button (you will get a hat) and the last flies in Webbed.
How to Get Hat Button
At the location on the map, slingshot yourself over this ridge at the top left.
Make sure you hug the wall as you fall so you don’t miss the platform.
Credit to MitchBeard
The Hidden Area with the Last 2 Flies
The entrace to the area is in the room with the first seesaw in the dungbeetle area
While standing on the ground you use the patch of grass on the side of the wall to sling yourself up in the tunnel where the chain is connected. If you’re successful you will be taken to a new area where you quickly have to launch a new web