Slightly off topic but the correct answer has been listed probably 30 times.
A lot of the race coaches where I work to this day don't trust shops to mount their bindings. I've mounted a couple pairs and my dad has mounted every ski he has owned as an adult himself too. I have a jig now but in the past I've had luck lining up the boot secured in the toe piece with something under the heel to keep it flat on the ski, mark and measure where the holes are, and carefully use a straight edge to draw lines, intersecting where the holes will be drilled. A drill press is nice to have if no jig cause you can get specific depths at a perfect angle, but I've never used one for skis. I just find the right drill bit for the screw, figure out how deep the hole needs to go, and put a piece of tape on the bit, stopping it from going too deep. Some people like to use a tap, but I feel like that over complicates things and doesn't let the threads bite as hard. Wood glue in every hole.
This is my experience. Don't mount your own bindings if you don't know what you're doing.