Cut open the cardboard box so it is flat
Cut out the shape of your roller coaster seat. We rounded the top, and cut an oval opening for you to insert self. Also left the side flaps to fold and be the side of the coaster.
Sorry...didn't take enough pics while making the rest of the costume. But we folded the bottom flat as a footrest, poked holes and tied a string to hold it in place.
Duck tape the crap out of it so it holds shape. Folded the sides and duck tape.
Poke holes on the sides in order to insert the rod, or here I just used a small PVC pipe. Then poke holes on the ends of the foam noodle so the PVC pipe can go through it.
Poked holes on the backboard of cardboard, top middle area. Used a string to tie noodle to the back.
Stuffed old pair of jeans with paper and attached old pair of shoes to the cardboard. I ended up using an old fanny pack to loop through and attach to myself.
We tried spray painting the whole thing after everything was done, but picked yellow and it came out really bad and splotchy. So we ended up using foil to wrap the whole thing, which worked out well.
We also used a patterned duck tape to do borders. I'm sure you can get real fancy with designs. But we were so last minute with making this costume.
Put it all together and you get something like this!
Finished product at the West Hollywood Caranval! Fanny packs were good to put extra duck tape for emergencies.
Tip: it's a good idea to frame it with PVC on the leg area, because we didn't and the cardboard kept hitting my shins and now I have a bruise.
Good luck and I hope that helps! Maybe you can try it for next years Halloween or a themed party.