Southampton began the second half with renewed intent, as Hawe fired straight at Lucca Benetton before Max Little was sent through, only for Benetton to race off his line and make the save.
At the other end, a golden opportunity fell to Chuks Okoli, who controlled the ball but blazed over from a few yards out.
The young Eagles were eventually rewarded on 55 minutes when Walker-Smith levelled the contest, Judd swinging in another dangerous corner for him to maintain his composure and sweep home.
Alonso then made a double change, with Casey and Judd withdrawn to manage minutes and workload.
Palace’s momentum was briefly stalled on the hour mark as a couple of Southampton players received treatment, but once play resumed they continued to probe, with the hosts surviving a series of shots and crosses midway through.
Approaching the 70th minute, Palace were launching wave after wave of attack. Kayden Moses and Angibeaud combined, with the former almost squeezing past Moody one-on-one, before Donte Martin scuffed a low effort into the defender.
Palace then took the lead moments later through Angibeaud, as Martin’s low strike from outside the area was spilled by Moody and Angibeaud reacted quickest to convert the rebound.
Angibeaud almost had a second when he battled through a crowd of yellow and blue shirts and looked to force the ball over the line, but Southampton’s defensive resolve held firm.
It mattered little, as Palace soon extended their advantage. With Judd off the pitch, Fasida took over corner duties and delivered a delicious inswinging ball for Walker-Smith to power home his second.