Because it is quite expensive, but not too hard to make one yourself, I decided to contribute another instructable.
4 pieces of 255 mm * 140mm * 9 mm (10" * 5.5" * 3/8") in nice solid wood (I used Oak), these will be the sides of the box
1 piece of 130mm * 130mm * 8 mm (5" * 5" * 3/8"). this will be the bottom, invisible and so it can be some MDF or plywood
~2000 bamboo skewers, 25 cm long (9.8")
Saw : only needed if you need to cut the 5 pieces yourself
Sander : ideally a Belt sander (I use the Bosch PBS 7 AE) for rough sanding, and a Orbital Sander (I use Bosch GSS 280 AVE) for finishing
Router (optional, I use Bosch POF 800 ACE)
Effort : takes about half a day
Cost : about 30$ - 25 euro. The Bamboo skewers I bought were 0.85 euro/100 pcs
You could modify the dimensions if you want to : I just made it to the size of some Oak I had left over, and the final result is about the right size for 3 to 6 knives.
Step 1: Assembling the box
1. Put one side on a flat surface
2. Glue the bottom on top of it : Align the bottom, and one corner (in my pictures I aligned the bottom right corner)
3. Glue one extra side at the opposite corner (so I added a side to the left)
Apply clamps and some weights (I often use books)
5. Glue the remaining sides, one by one.
6. Finish by applying a bit of glue to all inner joints with your finger.
Remark : ideally, the side will stick out just a little on all four sides. That's OK (better than being too small). This excess will be removed in the next step.
Remark 2 : It is important to take your time, take it one part at a time and let it dry enough. (my glue takes about 30 minutes, but 24h for full hardening out). So patience is your friend here !
To keep all panels exactly square, this could help