Foster and Chen teamed up for a victory on Saturday, in a race postponed from July due to a typhoon in the region.
"Morris, he's Taiwanese and it's a race he wanted to do at the end of the year," Slade explained to Supercars.com.
"HubAuto is actually a high-end car tuning business. We just got over there earlier in the week and we had a track day for his customers and friends, with Ferraris and Porsches and McLarens and things like that.
"We did that one of the days and then the race meeting, which was very low-key.
"Morris, the event being one of the bigger events in Taiwan, wanted to there with his own team and car and try to set some records and win the races.
"Nick did the first race with Morris, which they won and Nick and I did the second race and the same result.
"It was just good to go over, it's always fun to do different stuff and that's what I've enjoyed most, doing that this year; doing some different kind of racing, in different parts of the world, different tracks."
The outing takes Slade's tally of new circuits in 2018 to six, following the Blancpain rounds at Sepang, Buriram, Suzuka, Shanghai and Ningbo.
It comes amid a busy run for Slade, with trips to Japan and Taiwan falling either side of the Supercheap Auto Bathurst 1000 and Vodafone Gold Coast 600.
The Freightliner Racing driver's focus turns back to Supercars, and starts this weekend's ITM Auckland SuperSprint sitting 11th in the standings.
"It was good, just another experience, and something that I enjoy doing," Slade added.
"I'm mates with Nick, it's just a good bunch of guys in the team and it was good to see Morris the team owner, his home and be surrounded a bit more by his friends and workers."
Supercars stars check out MotoGP
Other Supercars drivers headed to Phillip Island, the scene of MotoGP's Australian Grand Prix.
Bathurst and PIRTEK Enduro Cup winners Craig Lowndes and Steven Richards went behind-the-scenes, with wife Lara and son Clay respectively.