The graphic paper turned out to have prints on both sides, so when folding the envelopes the insides of them showed another print.
This is really easy: put the wooden template on the paper and trace around the edges.
The instructions are even pictured on the template!Folding is done within seconds. I used a measurer to help me making straight folds.
Done. You could make labels or tags with the leftover scraps, great for gifts.