The B-side of a phonograph record.
Nice tune, what's on the flipside?
A necessary consequence or corollary of something; especially one seen as opposite, or as pro versus con.
Walking to work is definitely healthier – on the flipside, though, it takes twice as long.
The occasion when we meet again (e.g. when I return from work, etc.; said on parting); later or tomorrow.
See you on the flipside!