This is how the Christmas post is made:
Print out the template and transfer it to the Felt. The best way to do this is with a line-ex pencil or sewing chalk, as the lines disappear again or can be wiped away with a damp cloth. Cut everything to size
Cut the buttonhole slit cleanly. First sew on the button. Then close the sides by hand and sew around the buttonhole. You can use one Fineliners to write lettering or sayings on a white one and cut Paper it to size. Also cut Felt and Kraft paper trim to create a label. Stick the layers on top of each other and then stick it on the envelope.