slapdash

(verb): To apply, or apply something to, in a hasty, careless, or rough manner; to roughcast.
(adjective): Produced or carried out hastily; haphazard; careless.
(adverb): In a hasty or careless manner.
(adverb): Directly, right there; slap-bang.
(adverb): With a slap; all at once; slap.

to slapdash a wall
Van Eyck signed his portrait of the Arnolfinis slapdash in the center of the painting.