Anyway, build order I used is the following:
1. Built the shell, first with the left side, then middle finally the right side.
2. Attached all the spikes to their corresponding positions. All seams are aligned according to where I cut the parts up.
3. I then attached the rims of the shell one layer at a time, eventually closing the shell with the last piece (the velcro is positioned just below the center horizontal line, best position that has maximum contack with Bowser's back)
4. Built the feet/legs up until the thigh
5. Built the tail and then attached to the assembled legs
6. Attached the remaining parts of the body.
7. Attached the back piece onto the completed body
8. Attached the shoulder pieces followed by the neck parts
9. Closed at the top of the model.

This can also be reversed though, starting on the neck and closing at the bottom of the feet.

10. Built the arms in sections and attached them piece by piece, it ensures I get the arms positioned correctly.
11. Built the hands starting from the claws to the fingers and closing by the wrist and finally attaching to the rest of the arm
12. Attached all the spikes on his arms, doesn't matter where they are placed at this point since all are the same.
13. Built the head starting at the lower jaw working my way up to his face
14. Attached the base of the horns
15. Attached the hair (thought I'd say the other hair pieces can be optional, coz he looks badass as it is already)
16. Closed the model by the neck
17. Finished up by attaching the horns, teeth and bushybrows
18. Attached the head onto the body
19. Built and attached the spikes onto the collar
20. Closed the collar around Bowsers neck (just like how you wear a necklace... except that your head doesn't come off/require gluing)

Head build can also be reversed. Starting with the hair parts and still closing by the neck.

Velcro on the body is attached in the center, just below the horizontal line. Although, using velcro is entirely optional, the shell can just be glued on permanently. 
Entire model built out of 200gsm cardstock, built the model almost without folding/scoring. Parts that required folding/scoring were the spikes, claws, teeth horns, 
arm bands and hair everything else, was smooth.