"Crush" Turtle Cardboard Costume!

Recently, I designed a cardboard costume for someone who is in middle school. So my group, going along with the assigned theme of Marine themed costumes chose an individual theme of Finding Nemo. We all chose significant characters from the movie, and the character i chose was, my personal favorite, Crush! So I designed a sea turtle costume that a child could wear for say, a play production of Finding Nemo! But we did have some specifications and limitations for the costume such as:

Specifications:
Should...
-be made entirely out of cardboard
-use slotted construction
-be flat pack
-fit a middle school aged child
-use no adhesives

Limitations
Must...
-be safe
-be easy to assemble
-not require too much parental supervision
-use no adhesives
-be flat pack

Step 1: Materials List

Supply list
ITEM    MATERIAL    SIZE       REMARKS - PART
S1        Cardboard     6x3         Shell, shoulder straps

Tool list
ITEM TOOL                                 USE
TI CUTTING MAT                       To cut the cardboard on top of
T2 UTILITY KNIFE                      To cut the cardboard
T3 RULER                                   To measure lines and cardboard
T4 PENCIL                                  To make marks and lines
T5 PROTRACTOR                     To measure angles