"Slow Life" was written in two stages. According to bassist Guto Pryce the "electronic part" was composed by keyboard player Cian Ciaran "quite a few years" before its eventual release. The band had tried to fit this early, purely electronic, version on previous albums but had "never got 'round to it". By the time the group came to record "Phantom Power" they were anxious to release the song, however Ciaran was reluctant to leave it in its original form and encouraged the rest of the band to jam over his original track. According to singer Gruff Rhys the instrumentation was recorded "pretty much live" after which lyrics were written and the band's 10-minute jam session was "chopped ... up and made into a composed song" with the electronic section intact. Strings were later added by Sean O'Hagan. Rhys has stated that renting their own studio in Cardiff has given the band the ability to work on tracks such as "Slow Life" over a period of years—the group visit the studio almost every day and play: "the best parts on any of our records, I think, come out of a couple of us being in our little room in Cardiff at three in the morning, just wigging out and being ecstatic in the music."