I'm currently working on my bench and chopping mortises for the stretchers in the legs. Using laminated SPF 2x4s and a 12mm bevel edge chisel.
I do not own any mortise chisels. No drill press. No auger bits. So I'm asking for any tips on chopping better mortises.
The chisel is square, with a 25 degree primary bevel and an approximately 30 degree micro bevel.
I seem to wander a bit as I go, and my walls are a bit out of square. Is this just a matter of getting better with practice, or are there any tricks or techniques that are greatly beneficial?

Thanks.