Hey! I noticed that all the deck boxes with instructables were pretty high tech, and on a high schoolers budget that doesn't work out very well. So I set out to make my own that looked half decent.
All You Truly Need:
Cardboard
Cutting Utensil of Choice
Tape of Choice
Ribbon or Something Similar

Step 1: Cut Out Pieces

I realized I forgot to take pictures during this step, but essentially use a pre-existing box as a template. If you don't have that, here are the dimensions.
Top/ Bottom: 2.5"x3"
Sides: 2.5"x4"
Front/Back: 3"x4"
I left a small lip to use as a flap to tie the top down with. Do what you seem fit to do.

Step 2: Holes

Cut a hole in a the flap of the top and the side you deemed the front.

Step 3: Tape Them Together

I used an x-acto to get a nice edge with the tape. But tape it together along the sides that makes sense too. Observe the picture if you need help.

Step 4: Add the Ribbon

Cut off a length of ribbon, I used about 6". Weave it through the holes. You'll have to re weave it through a hole when you open the box, but oh well.

Step 5: Put Your Cards In, and a Divider

I used a piece of scrap cardboard as a divider.

Step 6: Finish

Now you're done! Leave any suggestions on how to improve it, as I'm probably gonna build another one soon.