After the tutorial for making the masu box, here is the tutorial for the lid 
The lid is made from a square the same size as the base. In spite of that, it needs to be slightly larger than the base so that it fits well. And I like my lid to be of a lesser height, so that it is easy to open the box. So with a few changes to the masu box, here is the masu lid!
I have explained in a lot of detail, so that all steps are clear. So though it make look like a lot of steps, it isn’t very difficult to do. Please drop a comment if any step is unclear.
Time Required: ~ 10 minutes
Difficulty Level: Simple
What is Needed:
- The second sheet of paper from the previous tutorial.
- Pencil or pen to make some markings
- Paper clips
- Glue
How to Fold:
1. The green square is the one that will be used for the lid.
2. Follow Steps 3 to 7 in the masu box tutorial, so that all four corners are folded to the centre.
3. Unfold the masu box completely and fold the four corners to the centre. The yellow one is the unfolded masu box. We need this so that we can fold the lid slightly larger than the base.
4. Place the 2 pieces face-to-face so that the folded corners are inside. We are going to align the pieces so that the folded edge of the lid lines with the first crease of the base (marked with a dotted line in the base).
5. Align the lid exactly on top of the base, as shown. Use a paper clip to hold the pieces in place. Once you get the hang of this, you will no longer need the paper clips
6. Turn it over so that the base sheet comes on the top and the lid at the bottom.
7. Now fold the part of the lid that is projecting out, over the base. You will notice that the edge of the lid does not line up correctly with the crease in the base. This will ensure that the lid is just a tad bigger than the base. Repeat Steps 5 to 7 for the remaining 3 edges.
8. Open up completely and place the paper so that the coloured side is facing you.
9. Fold in half so that one edge meets the other but don’t crease fully. Only crease from the edges to the next crease. Repeat for the other edge.
10. Unfold and turn over so that the white side faces you.
11. The next crease is going to be made using the 2 consecutive creases, marked in Step 11.
12. Fold and align the marked creases, so that you have a new crease mid-way between them. This will be the actual height of the box. You can play around with this fold, to make the lid a little taller or shorter than this. Repeat the fold for the other 3 sides.
13. Open up. You have now made all the creases necessary for folding the lid.
14. You can reinforce the crease made in Step 12 to ensure that the sides of the lid is sharp.
15. Fold opposite corners as shown and life up to form 2 sides of the lid. The corners will not meet in the centre, as in the base, but rather, will overlap and touch the opposite edge.
16. Now, the steps are the same as the base. Push in the the corners on the third side. The paper will naturally fold in on existing creases. Use paper clips, if required, to hold in place.
17. Fold down inside and crease well. 3 sides now completed.
18. Repeat on the 4th side. Crease the edges well. Since the sides are shorter than the base, you will need to glue down the parts that were folded in.
19. Refold your base. Cover the base with the lid, it should fit perfectly
Those boxes are awesome, thanks for the diagrams.
Thanks Peter
[...] Part of the tutorial, for making the lid, can be found here. [...]