AIm making a Toy Story themed cake for my son's 3rd birthday & I'm looking for suggestions on how to make the cardboard box part. Any insight will be greatly appreciated :)

You didn't say how big, and if the box is the cake, or if it is an empty box.  Gingerbread cookie dough should work very well for an empty box.  

Sorry my description was so vague..I was typing on a tablet lol!  I am planning on having the cake inside of the "cardboard" and the Toy story figurines popping out of the top.  I never even thought about gingerbread, which brings me to another point, how to I get the top flaps of the box to attach or do I bake them in 1 piece?   Thanks!!!

I would bake four rectangles for the sides of the boxes, and four rectangle for the "flaps".  Assemble the box first, then once it is dry, attach the flaps.  Royal Icing  dries hard and strong and you could be generous underneath where it wouldn't show.  .  Tint it the same brown as the gingerbread so it won't stand out.  Just prop up the pieces until the "glue" is really dry, probably several hours or overnight for the flaps.  l hope it works out!

I would make a cake for the box and cover with fondant or s50/50 panels make the flaps out of the same for the box and fill with your figures.  If you google toy story  box cake you will see how others did it! good luck and post pics!

Modeling chocolate panels make a great looking cardboard, and a strip of piping gel over it looks just like packing tape.  Open flaps will require some additional structure though.  Oh, and mini marshmallows make great "packing peanuts".  When I made the cake below for a friend's going away party, I had at least 6 people rush over and tell me that "someone set a box on the cake" - LOL!

wow!  That is awesome!

A

Wow!  That is fantastic!!!  Thanks for all of the suggestions ladies!  This cake was for my son's birthday & we had it at our house, so I ended up running out of time and ended up not playing with the box idea; I just did a simple toy story theme.