Flores was snapped up from Genoa last week.
Williams told the South Wales Echo: "He's a big lad.
"It ruined it for me because normally I say when you're this heavy you can't do well in the running, but he's blown that excuse after winning the bleep test.
"I've not seen him play, but you trust the gaffer's judgement and hopefully we have another good player on board and he's settled in well.
"We're a tight group here and fitting into that is arguably more important than what he does on the pitch, but early impressions are good."