Ashley Slater was born on April 20, 1961 in Schefferville, a mining town in northern Quebec, and grew up in Hanford, California. In 1977 he moved to Britain, settling in Edinburgh, where he joined the Regimental Band of the Royal Scots as a trombonist and stayed until 1983. After leaving the army he studied at the National Centre for Orchestral Studies in Greenwich, London. English Wikipedia describes him as Canadian-British, and his career has been built in Britain.

In 1984 he joined Loose Tubes, the cooperative jazz orchestra, averaging about 21 players, that grew out of a 1983 workshop run by Graham Collier and became the focal point of a 1980s revival in British jazz. Slater played bass trombone and tuba, and at live shows he acted as the band's compere, where his sarcastic wit became part of the act. Loose Tubes released Loose Tubes (1985), Delightful Precipice (1986) and Open Letter (1988, Editions EG, produced by Teo Macero), became the first jazz orchestra to play the BBC Proms in 1987, and disbanded in 1990. Slater was in the line-up when it reformed for concerts from 2014, and he is credited on the later Lost Marble releases Dancing on Frith Street (2010, taken from the band's last week at Ronnie Scott's in 1990), Säd Afrika (2012) and Arriving (2015).

Through the late 1980s and early 1990s he was also a sought-after low brass player across British jazz and its fringes. Wikipedia names him as the bass and tenor trombonist of choice for George Russell, Carla Bley, Andrew Poppy, El Sonido de Londres, Billy Jenkins, Django Bates and Andy Sheppard. The records back that up. He sang, played tuba and played bass trombone on Billy Jenkins's Scratches of Spain (1987), played trombone on Tony Coe's Mer de Chine (1988) and in George Russell's Living Time Orchestra on The London Concert, and recorded The Very Big Carla Bley Band at Bauer Studios in Ludwigsburg, Germany in October 1990 (WATT/ECM, 1991), followed by Bley's Big Band Theory, recorded at Angel Studios in London in July 1993. Sheppard used him on the big-band record Rhythm Method (1993) and on Delivery Suite (1994), a live set from Ronnie Scott's club.

Alongside the jazz work he led his own funk band. Microgroove, with an electric tuba in its line-up, made The Human Groove (Antilles New Directions, 1989), for which Slater wrote most of the songs, sang and played trombone, bass trombone and tuba. In 1993 he teamed up with Norman Cook, later known as Fatboy Slim, in Freak Power, a band with Cook on bass and the backing vocalist Jesse Graham that mixed acid jazz, funk, soul and trip hop, with Slater as baritone lead singer and trombonist. Their single "Turn On, Tune In, Cop Out" came out in October 1993 and reached No. 29 in the UK. Two years later it was used in a Levi's television advert, "Taxi," and the re-release of March 6, 1995 climbed to No. 3 on the UK Singles Chart, the group's only top-20 hit. The albums Drive-Thru Booty (1994) and More of Everything for Everybody (1996) both credit Slater as producer, singer and trombonist. The band split in 1999.

After Freak Power he recorded club singles as Dr Bone and made his own records, first Ashley Slater's Big Lounge (Plush/Patsy, 2002), recorded with the producer and drummer Steve Argüelles, the pianist Benoît Delbecq, the reedman Steve Buckley and the trumpeter John Eacott, and then Cellophane (released in Japan on Columbia in 2006 and in France on Plush in 2007). From March 1999 he was among the guest soloists who turned Gary Crosby's Jazz Jamaica into the Jazz Jamaica All Stars, and he plays trombone on their album Massive (2001). He also voiced the narration for the CBeebies pre-school series Boo!, which began airing in 2003 with a soundtrack in an early-1970s funk and R&B style.

From 2011 he has worked mainly in electro swing. Kitten & The Hip, whose first listed release is the 2011 EP Don't You Worry on Hed Kandi, released Hello Kitten (Pedigree Cuts, April 28, 2014), and Slater has since sung on dozens of club and electro swing singles by other producers, including Bart & Baker, Fort Knox Five and Glenn Gatsby. His most jazz-leaning solo record of the period is Bone Idol, Volume 1 (April 1, 2015), a trombone-led album of jazz, reggae, salsa and cumbia in which he plays everything except a few guest parts. In 2015 he also played trombone in the Spike Orchestra on Cerberus (Book of Angels Volume 26), a Tzadik album of John Zorn's Masada Book Two compositions, and in 2021 he appeared on the Electric Lady Big Band's Up From The Skies. His Discogs credits run into 2026, including a Heptet album on HipKit Records.

Slater is a jazz-trained brass player who spent most of his recording life elsewhere, and the elsewhere is where his name was made. He came up through an army regimental band and then Loose Tubes, a band that mixed jazz history with funk, Latin and hi-life and treated humor as part of the music. His best-known records, the Freak Power albums, the Dr Bone singles, the Big Lounge and Cellophane records and the Kitten & The Hip electro swing, sit in acid jazz, funk, club and pop territory, built around a husky baritone voice with a comic edge rather than around improvisation. AllMusic files him under jazz, and the Loose Tubes, Bley, Russell and Sheppard sessions, the Spike Orchestra record and Bone Idol, Volume 1 are the documented jazz side of a career that moved freely between that world and the dance floor.