We bought 3 canvas tarps at Home Depot measuring 15 feet by 12 feet. ($25 ea.)
We then sewed the 15 foot sides together; at the end of this we had one big canvas that was 15 feet by 36 feet. Now comes some measuring and cutting, so take your time measure twice and cut once. We lay the whole thing flat in our yard so we could see it... Staring at the left side of the 36' side measure 10' to the right then drew a line 3' up then, on that same line do a 2' mark then draw a line back to the side making a rectangle that we will Call cut A-1. Do the same thing one the right side of the canvas we will call this rectangle A-2 (see diagram) * each square = 1'
Now cut out the two 10' by 2' sections and save these two pieces. Cut up the line to the 3' mark.
Take the two pieces that you just cut off and sew them together along the 2' side; move the piece to the back where it is sewn to the center of the 36' side making the center now 17' ( see diagram) *each square = 1'
Next find the center of the side you just removed A-1 and A-2 from and draw two lines 2' apart from the top of those lines 1 1/2' back to the center it will make a big M shape ... cut this part out ( see yellow area of diagram ) we the sewed a triangle piece of canvas where the bottom of the M where the smoke flap poles will go into.(see the teepee picture)
Its a good idea to reinforce all areas that end in a cut.
You now have your smoke flaps.