Here's a guide to making a folded, non-glue or tape, seed envelope. The construction can take a fair bit of abuse without falling apart. It also has the advantage of being customisable to the size required, within reason. I cannot take the credit for this as I believe that this design has been used on spice markets for a very long time. I recommend that you practice making an empty one first, prior to making one containing seed.
1. Place a square or rectangular sheet of paper on a flat surface. For the purpose of this guide I have used a square note (9cm x 9cm) which is a good size for small seeds:
2. Fold the paper approximately 1cm from below the centre line, to allow for a 1cm flap at the top:
3. Fold the flap at the top down:
4. Turn the paper over, so that the flap is now facing the table, at the top:
5. Fold the top right corner down diagonally to form a triangle:
6. Fold the bottom right corner up diagonally to form another triangle:
7. Tuck the bottom right corner triangle under the flap:
8. Write the seed name on the opposite side of the envelope.
9. Add seeds to the open (left) end:
10. Repeat steps 5, 6 and 7 but for the left corners.
11. This final step isn't really necessary for the integrity of the envelope, but it tidies things up a little. Fold the little outwards facing triangles, which have formed at the bottom of the flap, underneath the flap: