1.) Trade or waive Cedi Osman or Reggie Bullock
If the Spurs plan on signing Cissoko and Barlow to NBA contracts, they will have to either waive or trade wings Cedi Osman and Reggie Bullock. That could mean yet another deal involving the Spurs, though they would have to wait until September before being able to aggregate their salaries in trades.
As a result, barring a one-for-one or one-for-none deal, it may take some time before the team could officially sort out their roster situation. Another possibility would be the Spurs simply waiving Osman, despite his shooting ability. That would allow San Antonio to hold onto Bullock to start the season, with the goal of moving him later on.
Doing so would allow the Spurs to sign Cissoko to a multi-year deal in addition to bringing Barlow back on a two-way contract, leaving another two-way spot open. Later, the team could move Bullock near the trade deadline for multiple seconds, much like they did with Josh Richardson. Better still, that could also pave the way for the Spurs to convert Barlow to a standard multi-year deal similar to what the team did with Bassey last season.
All in all, the Spurs will need to do some maneuvering to trim the roster after the Payne trade. Luckily, making a two-for-one trade and waiving Stephenson, Birch, and Osman would be enough to get the team's roster down to 15 NBA players.