The Envelope Punch Board has the measurements for creating a matching 3″ x 6″ envelope – this bit is no problem – but then on the resulting envelope, the long flaps are too long and they overlap the opposite edges of the envelope.
Fold back one of the short triangle flaps and insert into a Paper Trimmer so that this edge is against the top. Line up the envelope score line approx. two thirds of the way across the trimmer (for this envelope that was around the 2″ mark) and cut away the excess.
Turn the envelope around, fold back the other short triangle flap and insert into a Paper Trimmer again. This time, line up the envelope score line approx. two thirds of the way across and then add approx. another 1/4″ – 1/2″ before trimming away the excess.
This results in an envelope that still looks smart but has sufficient overlap to close easily.
Hope this helps with your long envelope making.