This ible doesn't take much skill but it will take some time especially if you need to make more than one block. There's paint involved so I'd paint outside or put down sheets or paper.
Step 1: Materials
Cardboard (a lot of cardboard).
Masking tape .
Paint. Black (or black electrical/ masking tape) and the block colour.
Step 2: Tools
A good pair of scissors
A tape measure
A pencil or sharpie
Step 3: Scavenging Time!
Great places to look are:
Wholesale food shops
Furniture shops and white goods stores
The houses of people who have just gone on an ikea binge
Bad places to look:
Greengrocers and smaller shops
Bond villain lairs
You want card which hasn't been in direct contact with food, has been stored in a dry place and has some structural integrity.
Step 4: Measuring Up
First, measure your shoulder width plus a bit of wiggle room, then times it by three for the height OR measure from shoulder to knee and divide by three (checking this length is wide enough to accommodate the shoulder span).
Step 5: Make a Net for the Costumes
Mark out each of the faces of the block on your cardboard, if you are limited in cardboard you can do this in multiple sections and tape/glue them together.
Once you mark out the basic shape. add tabs, a few inches wide, to the edges then cut it all out.
An alternative to the tabs is to mark out the faces and cut them all out, then cut strips of cardboard to join the edges together.
Step 6: Putting It All Together
First, lay the faces flat and tape the 4 sides together, use masking tape and clothes pegs to hold them in place then glue all the flaps down.
Once the glues set, stand the costume up and repeat for the final edge, you might have to get in the costume to do this. Add the top face last.
finally, cut holes for your head and arms.
Step 7: Add Paint, Lots of Paint.
Cover the entire box, it also helps to masking tape the corners for strength and to hide the joints.
You will need to do a few layers of paint, make sure it dries between each layer so the cardboard doesn't get soggy.
finally, to get the black edging on the blocks you can either use paint or black tape.
Step 8: Have a Block Party!
p.s. sorry for the lack of pictures, I made this a while ago and didn't have the foresight to record the process.