"The past three or four weeks have been really tough. All of the boys have been training hard. We're all just happy to be selected for the World Cup squad as it seems like we've been working towards this for a long time.
"I think we started last June so it has seemed at times the season has gone on and on. It's been a full year in preparation for the World Cup.
Williams still vividly remembers the amazing scenes from four years ago when Wales stunned the world.
"Winning the World Cup is probably the best moment in my career. I can remember it clearly, especially when you see a few clips on television. I saw Lee Beach do an interview a short while back and he was mentioning a few stories which recaps the memories - it's always a good feeling remembering those special moments."
Williams is optimistic Wales can replicate their shock result from four years ago but is taking nothing for granted.
"We've got a good bunch of boys plus we've got a good group in Moscow so hopefully we can regain the trophy.
"We' been together for a full year, got a fully fit squad which is really important and we've also got the likes of Gareth Davies coming back into the squad to strengthen the side so we are looking forward to it."
Along with Uruguay, Wales take on Tonga and Fiji tomorrow in their remaining pool games while the quarter-finals begin on Sunday.