Flores was added to the White Sox's 40-man roster Wednesday, Mark Feinsand of MLB.com reports.
Flores tossed 78.1 innings for Double-A Birmingham last season, recording a 3.33 ERA with a 1.14 WHIP. Although he's shown some promise at the Double-A level over the past two years, he'll still likely need to face some more significant competition before being considered for a major-league role. Wednesday's addition to the 40-man roster shields him from the Rule 5 draft.