2.) Waive Lamar Stevens and Khem Birch
Not every move will require the Spurs to make a two-for-one deal to free up roster space. They could look to waive at least a couple of players, with Khem Birch and Lamar Stevens being the most likely players to be waived before the start of next season.
With plenty of guard and big man depth, the Spurs are unlikely to need either player, so they could be waived sooner rather than later to give them a chance to catch on with another team. Losing Birch and Stevens, in combination with the aforementioned two-for-one deal, would allow the Spurs to get down to 15 NBA roster spots, the maximum.
That could be all they would need to do, aside from signing Cissoko and Barlow to the two remaining two-way roster spots, with Sir'Jabari Rice already filling one. That is certainly possible, though the team's recent track record suggests that they might want to lock either or both players up on cheap long-term deals.
They did the same with Charles Bassey and Julian Champagnie. They also signed Tre Jones to a three-year deal after he was taken 41st overall in 2020. That would seem to bode well for both players and suggest that the Spurs may need to clear out additional roster space.