Here is a really easy way of quickly folding your own envelope from a A4 sheet of paper. This is to fit an A6 size greetings card. No template or cutting required. The key part is positioning the card as shown in the first step below. It doesn’t need to be exact but you want it to one side, on an angle and with a small margin around all corners. Once folded then just secure the last flap with either a square of double sided tape, a sticker or, as I’ve done here, a wax seal (flamingo!). Practice a couple of times with printer paper first if you’re not sure.