Cutting flue pipe hole in attic and roof

New to installing a wood stove. Had help but he turned out to be more harmful than helpful. I have a Regency F1100 certified stove that is close clearance with double wall pipe. I need to cut the hole in the ceiling as well as the roof and want to get it right.
I also looked up flashing and its very expensive just for the roof jack but a local hardware store said they can order a plain Jane galvanized one like everyone use to use for under $20 and need instructions on how to install it without a leak. The pipe is metalbestis 6in double wall for attic and roof.

Here's the site for the company that I bought all my pipe and supplies from.

https://www.northlineexpress.com/chimney-pipe-stove-pipe.html

One very important point.  You said you have double-wall pipe.  That is OK untill you pass through the second floor, and up into the roof.  As soon as you pass through anything made of wood, you MUST use triple-wall pipe, which continues right up to the chimney cap.  This is a very important code requirement.  The site will cover almost all your code adherence questions.

I have to say that the triple-wall pipe is fantastic!  Sitting on the second floor, I can grab hold of the chimney pipe and not get burned.  The protection is that good!

Thanks for the reply. The codes here in Oregon only require double wall through the ceiling and roof as long as the hole is 2 inches away from the pipe, so if you have a double wall 6 in flue pipe the outside diameter is 8 inches so the hole needs to be 12 inches.

What material is your roof made of?

Plywood sheeting and asphalt shingles. I went into town and discussed it with the store that sells and installs wood stoves here...

Maybe worlds best practise is worth considering, IE Triple flue past timber.
Its easier to seal anyway than straddling a 2 inch gap.

I can tell you the flexible roof jacks are faster to install and seal better.
I notice they cost about $US 45 compared with the $20 you quoted.