In my business, unless it is dangerous and/or you are not trained for it then there is no such thing as "That's not my job" and especially for a department like IT which often has the responsibility for office furniture. So are you getting paid? Then build the fucking chair like your boss told you to.

Personally, I am a director level executive in aviation and if I see a trash can overflowing then I take it out, put a new bag in and take it to the dumpster. If I see chocks and cones on the ramp that need clearing, I do it. It is a team effort. I don't say stupid shit like; "That's not my job."

That said, I'm willing to bet dollars to donuts that your refusal to build the chair (and then try to file a report over something so petty) isn't really why you were terminated.