Years ago I made pine beds for my daughters, the wood was reclaimed or bought from the local DIY. Lots of mortices in 4x4 timber so I bought some Sorby morticing chisels in the required sizes. I cut the mortices on the floor in the hall sitting or kneeling astride the timber and the work went quite well, the first half a dozen were the worst. The Sorby steel was OK but not great and I bought some Japanese Chu-Usu Nomi which after I had sorted the bevel out I found were far superior. If I were to do it again I would probably make a pukka morticing bench whatever they are called, it is not a case of hitting the chisel harder but using a quality sharp chisel. The position I adopted cutting these mortices also helped me keep the chisel vertical, brought stronger muscles into play and I would certainly recommend it if working with deep mortices in thicker timbers. No Internet in those days!