How was this costume created and where can I go to do something similar myself?

The expanding foam is used as a casting medium and it’s not the sort of casting you start out with.

Obviously a project like this takes lots of time and experience and I’m sure even with it you have to expect that somethings won’t work right the first time. If it’s something you’re interested in pursuing in the long term you’ll want to get into sculpting and moldmaking. Both are a craft and aside from just diving in (which is good) you should also consider checking out relevant craft books and classes in your area to help learn techniques. Theater tech and prop-making techniques would also be a good place to look.

It was created the same way packing material is created which fits the product perfectly. You need molds to spray extruded foam into.

In the old days, we used to take the commercial packaging foam we found and cut it up into the pieces we needed to resemble animal heads, or in your case, armor plates.

@fundevogel : Craft books would be great, but what is this called? “Foam casting”?

Oh, you already said it. Sculpting and moldmaking. Sorry.

@jellyfish3232 This is one way to make similar armor.

This is a great source

I noticed that it took the costume maker 3 years to make the costume. Will you still want it in 3 years? You can build a card board one, building up cut out layers and and finishing it with siver paint. It won’t look as professional, but you’d have a fun costume for next Halloween.