The 27-year-old joined the Hammers from Swansea City last season in a record-breaking deal, but could only give out an average performance following an injury he sustained on his debut against Chelsea.
He played 25 games, starting 19 times and scoring six goals, half of his tally in the previous season.
"We're working hard here, trying to get fit, working together and getting to know each other, so it's sweet. Pre-season is something which is very, very important and, for me. I've not been able to have a real pre-season for a long time because of international games.
"I have always been coming back later, so to start the pre-season with the squad is quite good," he added.
Ayew admitted he only attained full fitness towards end of last season.
"It was not my optimum, but I was getting there bit by bit by playing games," he said.
"For me, it was a shame the season came to an end because I was starting to feel better after my injury. I need to continue working hard and doing what we were doing at the end of last season and I'm sure I will get back to my best physically and everything will be okay."