There will be 12 pairs of players who never play together. Also there will be 18 pairs who play together twice. You could take advantage of this 2nd feature by assigning players into three ability groups, then each of the repeated matches would be with someone of equal ability.
( 9 7 6 5) (1 8 4 2) (3 11 12 10)
(10 8 7 6) (2 5 1 3) (4 12 9 11)
(11 5 8 7) (3 6 2 4) (1 9 10 12)
(12 6 5 8) (4 7 3 1) (2 10 11 9)
Within the player groups (1 2 3 4) (5 6 7 8) (9 10 11 12), all pairs play together twice.
The following pairs don't play together:
1 6
1 11
2 7
2 12
3 8
3 9
4 5
4 10
5 10
6 11
7 12
8 9