Breaking down a lamb "square shoulder"
You can treat the square just like a plain shoulder roast (assuming both with bone in?)

While boning it out may make carving easier, the less you cut it the better it will cook (speed, moistness etc.)

A whole lamb can be butchered with just a decent boning knife if you know where to cut. You may need a small saw to section the large bones depending how you cut it

For the square shoulder you need to knife out the rib, backbone (if attached), and then the blade. All from the non meat side of the roast