for a 12-team conference playing a 9-game schedule would be a reasonable option (based on the fact that the Big 12 seems to be leaning towards no divisions and a 9-game schedule). That would essentially give the Big 12 three 4-team "pods". Looking at geography, I would see 2 viable options:

Option 1:

East Pod: UCF, West Virginia, Cincinnati, Iowa St.

South Pod: Houston, TCU, Baylor, Texas Tech

North Pod: BYU, Oklahoma St., Kansas, Kansas St.

Option 2:

East Pod: UCF, West Virginia, Cincinnati, Houston

North Pod: Iowa St., Kansas St., Kansas, Oklahoma St.**

South Pod: BYU**, Texas Tech, TCU, Baylor

**Option 2a would be to swap Oklahoma St. and BYU

The idea behind this pod idea would be that you play the 3 other teams in your pod every year, and then you either play play 6 of the 8 teams in the other pods in some way (either a 4/2 split or a 3/3 split).  Note that while the PAC-12 technically has 2 divisions, their scheduling essentially uses this pod system:

Pod 1: Utah, Colorado, Arizona, Arizona St.

Pod 2: USC, UCLA, California, Stanford

Pod 3: Washington, Washington St., Oregon, Oregon St.

**Even though the California schools span 2 divisions, they have come to an agreement to allow them to play each other every year.  That mans that USC and UCLA play every team in pods 1 and 2 (7 games) and 2 teams from Pod 3.  California and Stanford play teams in pds 2 and 3 (7 games) and 2 teams in Pod 1.

Pods 1 and 3 play 3 opponents from each pod (while ensuring 2/3 of their Pod 2 opponents are their divisional teams).

Also, while this is how the schedule would lay out in a 12-team Big 12, the reality is that there will likely be 2-3 seasons where the Big 12 is at a 14-team conference with Texas and Oklahoma still in the league.  I'm not sure how the above would work with that setup.