Giles' second NBA season was much like his first, but more efficient. Although in many ways he nearly replicated his rookie year's stat line by averaging 6.9 points, 4.1 rebounds and 1.3 steals across 14.5 minutes, he improved his field-goal percentage by more than five ticks to a sharp 55.4 while drastically improving his free-throw shooting (77.6 percent, way up from 63.7). He played in 46 games for the Kings, starting 17 times after coming off the bench for his entire rookie campaign. On Jan. 7, Giles received his first NBA start, and he delivered eight points, eight rebounds and a steal in 16 minutes of playing time. Come February, Giles became a regular in the starting rotation, opening the game on the court in 14 of Sacramento's last 16 contests before the season was suspended. Over that span, Giles tallied 10.4 points, 6.3 rebounds, 1.3 assists and 0.6 steals over 21.0 minutes per game. He set a career high with a dozen rebounds Feb. 8 against the Spurs, then did it again two weeks later against the Clippers -- this time adding 14 points for his first NBA double-double. Giles went on to double-double again in the bubble on Aug. 11, notching 12 points and 11 boards against the Pelicans.

After sitting out the 2017-18 season to improve the strength in his knees, essentially taking a redshirt season, Giles made his NBA debut in the 2018-19 season. The Kings gradually increased his workload as the year went on, as he averaged 9.7 and 9.4 minutes per game in November and December, respectively, before seeing his playing time jump to 16.6 minutes per game in January, 15.3 in February, and 18.6 in March. The former 20th-overall pick was then shut down in April as a precaution. Overall, the 20-year-old averaged 7.0 points and 3.8 rebounds over 14.1 minutes per game. Giles recorded his first double-digit scoring effort on Nov. 12 against the Spurs. Later in the month he had back-to-back 10-point nights against Golden State on Nov. 24 and Utah on Nov. 25. He scored a season-high 20 points against Atlanta on Jan. 30 while also adding seven rebounds and one assist. Giles recorded a season-high nine rebounds in 18 minutes in a 119-116 win against Oklahoma City on Feb. 23. He scored in double-digits on three consecutive games twice, from Feb. 4-8 in games against the Spurs, Rockets and Heat, and again from Feb. 27-March 4 against the Bucks, Clippers and Knicks. His totals were especially impressive on a per-36 minute basis, where he averaged 17.9 points, 9.7 rebounds and 4.8 assists.