Green’s Dictionary of Slang

build v.

1. (orig. Aus.) to prepare, of food, drink, a marijuana cigarette etc.

[Aus]H. Lawson ‘The Darling River’ in Roderick (1972) 90: I reckon you can build me your national drink.
[US]C.L. Cullen Tales of the Ex-Tanks 382: He [...] had built flapjacks for a mining outfit.
[US]S. Ford Torchy 177: I misses my swell outfit, the one Benny had built for me to wear at his weddin’.
[US]T.A. Dorgan in Zwilling TAD Lex. (1993) 66: Yes the chef at the Grunewald in New Orleans showed me how to build this and it’s some powder.
[Aus] in Nina Pulliam I Travelled a Lonely Land (1957) 217: If I had my dilly-bag now I’d build you a damper.
[US](con. 1949) G. Pelecanos Big Blowdown (1999) 250: The tender, who’s nothing more than a pimp who builds drinks on the side.
[US]A. Mansbach ‘Crown Heist’ in Brooklyn Noir 124: Enough for him to [...] commence to building one [i.e. a cannabis cigarette].
[US]C. Black ‘Topless Vampire Bitches’ in C. Rhatigan and N. Bird (eds) Pulp Ink 2 [ebook] Turning back to the spliff I was building.

2. (US Und.) to create confidence or apparent friendship, for the sake of enticing a victim; thus built up adj.

[US] ‘Und. “Lingo” Brought Up-to-Date’ L.A. Times 8 Nov. K3: BUILD: TO work up a confidence, or a pretended friendship.
[Aus]F.J. Hardy Four-Legged Lottery 60: Jim said [...] expressing less confidence than he felt: ‘We’d better not get too built up. We’re not the only pebble on the beach.’.

SE in slang uses

In phrases

build pigpens (v.) [the practice of woodcutters who pile the wood on their carts in the shape of a pigpen; thus making the pile, which is hollow, appear larger than it is]

(US) to deceive, esp. for a merchant to cheat a customer.

[US]Randolph & Wilson Down in the Holler 231: build pigpens: phr. To deceive someone, to cheat a customer.