Endings go in the same place as a turnaround, and they usually have the same harmonic structure. In fact, the simplest way to construct an ending to a tune is to use a turnaround, but instead of going to the V chord for 1 bar, you simply go back to the I chord.
Even when a turnaround is used, the RHYTHM is usually changed to what I call a "standard ending rhythm". When a song has been going on for a while and you hear this rhythm, you know that it is about to end. It sounds like this:
Putting it with the bass notes of a turnaround sounds like this. Notice the last measure simply walks up the notes of the C major scale to return to the I chord (key of C):
You can put any licks that you know for the right hand over either left hand sequence. There is only one rule that is usually adhered to - Leave the first 1/8 note for the LEFT HAND ONLY to play. The last two chords in this example are Db9 (or C#9) and C9:
You can also simplify the last bar to return almost directly to the I - chord via a half step passing tone above.