Here's my approach...
No template. There's slight but sufficient variation between all the structures involved that you really want to trim it to fit. And it's not that bad at all if you take a methodical approach to it.
Here's what I did, which worked well:
First of all, if you haven't already trimmed the flap inboard edge to clear the fuselage, do it now before you proceed.
Now, forget about that little guide notch that Van's pre-punches in the fuselage side skin. It's pretty close to the right place, but not all that useful as a starting point. For a better starting point...
... install the rod end bearing only (no pushrod) into the flap, and install the flap to the wing. Let the threaded shank of the rod end bearing lay back (facing aft) out of the way. Now hold the flap up as far as it goes, which will be limited by the rod end bearing hitting the bottom fuse skin. Mark its outline on the fuse skin, and then cut it out.
Now the rod end bearing should be able to slide through the fuse bottom skin (shank first) until the stud portion of it that threads into the flap hits the fuse side skin. Again, mark it, then cut. Be conservative (don't cut too much at once) and allow for a couple of iterations of cutting, checking, marking and cutting some more. Get to the point where the rod end bearing can penetrate the fuse with no interference, and so the flap can go all the way up.
Now with the flap in the "up" position, install the push rod connecting the flap to the torque tube. Start to lower the flap gently until the push rod hits the side of the hole in the bottom fuse skin. Mark the area of interference, and trim. Now you should be able to lower it some more. Repeat until you can lower the flaps all the way down with no possible interference anywhere along the way. You'll end up with kind-of-a peanut-shaped hole.
This process is a bit iterative, yes. But this way the hole will be no bigger than it needs to be. You won't get results that accurate from copying a template from a different airplane, or even from one side to the other of the same airplane.
Good luck.