slap onto

slap onto

To apply something to oneself or something else very hastily or haphazardly. A noun or pronoun can be used between "slap" and "onto." Don't just slap makeup onto your face like that—you need to learn how to put it on properly. I can't understand why this artist is so revered. It looks like he just slapped paint onto the canvas and left it at that.
See also: slap
Farlex Dictionary of Idioms.

slap something onto someone or something

 and slap something on
to place something onto someone or something by slapping. Tim slapped a sign onto Gary that said "kick me." Tim came up to Gary's back and slapped on a sign.
See also: slap
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • slap in
  • slap on
  • turn around and (do something)
  • turn round/around and do something
  • slap down
  • slap
  • (I) wouldn't (do something) if I were you
  • slap together
  • (you) wanna make something of it?
  • (mother) nature's (something)
References in periodicals archive
Summary: Domino pieces rapidly slap onto the table in the opening salvo.
The People's Teahouse
This comes on top of the so-called disloyalty charges that some banks already slap onto customers who use other cash machines.
Voice Of The Mirror: Cash and grab
To combat such bruising blows to skin and confidence Laboratoires Garnier have developed an emergency patch to slap onto the offending pimple.
Post Style: What's new - Hands up for a dollop of extra care