Interested in learning more music theory? Check out my eBook - Applicable Music Theory For Gospel Musicians . Major 7 piano chords may be played with the typical four note voicings:
C E G B C
E G B C C
G B C E C
B C E G C
Or you may treat the Major 7 as iii over I. In words, E minor over C:
E G B C
G B E C
B E G C