I am left handed. I have read several well respected books that include handwriting instruction. Some books insist that left handed students tilt their paper to the right, just the opposite of students who are right handed. I disagree with this advice.
Although it seems to make sense to do so, since students are writing with the opposite hand, the logic does not hold up. That is because lefties still write from left to right. If left handed students wrote from right to left (basically, forming all of their letter backwards), then tilting the paper in the opposite direction works. I've tried it.
If you force left handed students to write with their papers tilted to the right, one of two things will happen. First, they might write with a backhand. The letters will slant backwards. Second, they might pull their right shoulder back, pull their left elbow forward, and curve their wrist so that they can write with the letters in the correct letter position. The second option is what I did throughout early elementary school. It was uncomfortable for a short period and painful for longer periods to write this way.
The secret is for both right and left handed students to tilt their papers slightly to the left. Right handers will have their hand, wrist, and forearm in a line parallel to the side edge of the paper. For left handers, their hand, wrist, and forearm will not line up with the edge of the paper. Instead, the left hand and left edge of the paper will form a tepee shape.
This way left handed students can write comfortably.