Hi!
This method is so simple, fast and accurate that it should be well known but looking around the internet that doesn't seem to be the case. Start with layouting the hole you want to have in the template, then make saw cuts partially through the template, just touching the inside of the layout lines. Remove most of the waste using jigsaw or bandsaw and finish up with a trim routing bit. Since I learned this method I use it for almost all templates, small tasks like hinge recessing template up to really large templates. One big advantage compared to for example festool mfs adjustable template (and clones) is that steps and angled lines is no problem, neither is large round in the corners. Four pics that describes the process quite well and final picture how finished template looks from other side, more info in the video. If you think the video is long I describe the method quite well in the first two minutes.
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