It came in a cardboard sleeve. That's a standard 8" (20cm) chef's knife for scale: I had to use something to get the packaging open...

Out of the sleeve it looks like this:

The black panels are held together halfway down the short sides, so it opens out into an X-shape. Two triangular side panels fold out to brace, revealing a charcoal grill which you slide out from parallel with the side and insert as a cross-brace, further stabilising the X:

The silver grill you could see in the second photo is a three-way fold which opens out to form the actual BBQ area for food and adds yet more bracing to the X to make sure it hold its shape. And there are you are, ready to go:

And just to prove I could do it in almost no time at all, here it is repacked and ready to take away with me:

I'll be honest, the build quality is not quite up to the standards I expect from Firebox, but this only needs to survive two or three camping trips to pay for itself in money I won't spend on on-site caterers. I have 7 or 8 trips planned this year, so even if I end up ditching it at the end of the summer, it's been a very worthwhile investment.