Carefully design your robot in CAD.
Then: poorly machine the parts
(make sure to drill a lot of unnecessary holes). Do a terrible job welding
(the key here is to make sure nothing comes out 90*, while maximizing burnthrough and blobbyness).
Duct Tape. Use it wherever possible. When wiring, make sure to use as much wire as possible and tie it in great nots all over the bot.
...Then cover everything in
plastic panels so no one notices
What? You think I'm joking?