A variation of "I'd tap that", used lightly, and referring more to the oral aspect of sex.
*walking around the local shopping center*
Terrance:DudeCasey flattened Danni's bread
Phillip: OMG! NO WAI!*fart*
*in the hallway*
Peascoe flattened the hell out of Cynthia's bread
*McDonalds*
Demond: See that hot chick?
Eric: Yeah, I'd flatten that bread!