When doing cantilever cards i don't use a template as i base my aperture round my main focus.
In this case a floral pyramage.
I took the gold piece of card i have matted under the pyramage and placed it where i wanted it on the wrong side of the card. I do this while i have my piece of card sitting on my eazi scoreboard as i use the lines as a guide at this point i score my card along the centrefold line (in this case A4 as finished card is A5 size). This helps me to line up where i want the aperture i work better by sight than by measuring well most of the time haha. Once you have decided where you want your centerpiece draw round half of it the half nearest the outside edge of your card then draw a fourth side down the gatefold line so you have a shape half the size of your main focal point. I then cut out this shape and place this card on top of another sheet of card the same size , lining them up exactly or your card won't work properly. Then draw carefully round 3 sides of your aperture the edge nearest the edge of your card the top and bottom only. You need to make sure your drawn lines are as close to the aperture as possible so both pieces of card match up.
You then cut along the 3 sides and score this card 3 times along both gatefold lines and half fold but you should only score above and below where you cut so that your cut bit sticks out and has no score on it. This is where your focus will go.
Then join both cards together back to back especially important if you ar using textured or patterned card.
This is the one occassion that i like the eazi score board the rest of the time it drives me mad with its continental edge lol. As you can see in the pic the folded inside of the card pokes out over the edge of the front, so i make a feature out of it and ink it in a co-ordinating colour i mirror this on both sides so when it is opened each long edge and both sides of the mountain fold are inked i also find it helps to break up an expanse of plain colour.
The front of the card i inked with distress ink in old linen then i used a little cats eye shaped chalk ink pad in amber clay and dabbed that lightly over the card. Added my pyramage and matt to centre and added some paper flowers and flower gems to finish. The gem flowers were clear ones which i used permanent pens in orange and gold on.