why not leave it whole, spread the ice cream, top it. Put in freezer to slightly harden, and cut into squares. It just seems easier.
The brownies were fairly thick so I found it better to split them and place the ice-cream in the middle. Mine didn't look nearly as perfect as the picture, assuming these are real. The ice-cream got soft and made it hard to assemble after awhile. Way too much work. Next time, put ice-cream between two chocolate chip cookies.