Have a look at the schedules that you can
find here.
Split the one for 12 players like this (where P1 to P12 are the 12 pairs of lanes and the blocks of 6 & 5 rows are the 11 rounds).
P1 P2 P3 P4 P5 P6
(F D) (J K) (A G) (E L) (C H) (I B)
(E J) (H F) (B K) (I C) (L G) (A D)
(L I) (G B) (J H) (K D) (E A) (C F)
(G C) (L A) (I D) (J B) (F K) (E H)
(H K) (I E) (L C) (F A) (D B) (G J)
(A B) (C D) (E F) (G H) (I J) (K L)
P7 P8 P9 P10 P11 P12
(D H) (B L) (C J) (A I) (K E) (F G)
(K G) (F J) (D L) (B E) (A C) (H I)
(C E) (K I) (H B) (L F) (G D) (J A)
(I F) (E G) (K A) (D J) (H L) (B C)
(J L) (A H) (G I) (C K) (B F) (D E)
You can use the same schedule for the 2nd group of 12, just flip over the assignments P1-P6 and P7-P12.