The vessel is expected to set sail by 2026.
The landmark moment marks the beginning of a new chapter for the ferries, which have been sailing on the River Mersey for more than 800 years.
Following the all-important steel cutting, construction is now underway at Cammell Laird's Birkenhead facility.
The hull is beginning to take shape thanks to more than 90,000 metres of welding, and a total of 327 tonnes of steel.
From platers to welders, 25 apprentices are investing a total of 17,000 hours on the history-making project.
Steve Rotheram, mayor of Liverpool City Region, said: "The world-famous Mersey Ferry has inspired books and songs and has been making waves in our city region for more than 100 years. Today, we begin its next chapter.
"As a staple of our heritage, the ferry has connected millions of people over its 800-year history, many of whom will remember the first time they hopped aboard.
"We want future generations to experience that same feeling, which is why we're investing in a new boat and why we've developed a 20-year strategy to keep the Mersey Ferries on the water for many more years to come."
David McGinley, chief executive of APCL Group, added: "Cammell Laird has a long history of supporting Mersey Ferries, our facility has built 15 of the vessels, dating back to 1836, as well as helping to maintain the current fleet.
"This new project will be built by apprentices working alongside our highly- experienced teams to create a state-of-the-art vessel that we will all be able to enjoy for decades to come."
In September, images and a video were unveiled, showing what the ferry will look like.
