During the summer of 2018, Slaten played for the Eau Claire Express of the Northwoods League, going 7–1 with a 1.58 ERA and 70 strikeouts over 57 innings.
[8] Slaten spent the 2022 season with the Frisco RoughRiders of the Double-A Texas League, going 1–6 with a 6.93 ERA and 64 strikeouts over 50+2⁄3 innings.
[10][11] He was promoted to the Round Rock Express of the Triple-A Pacific Coast League in September and posted a 1–0 record with a 1.08 ERA over 8+1⁄3 innings.
[12] On December 6, 2023, the New York Mets chose Slaten with the seventh selection in the Rule 5 draft,[13] and traded him to the Boston Red Sox in exchange for minor-league left-handed pitcher Ryan Ammons and cash considerations.
[14] Slaten was added to Boston's Opening Day roster,[15] and made his major-league debut on March 30.