Imagine a line coming directly from the sun to the surface. You want the panel perpendicular to that line. Sunlight has 1000 watts per square meter depending on various factors. Solar panels are about 22% efficient at best, you need every advantage you can get! Glad to help. I’ve been off grid for a few years, learned a few things along the way.
Discussion
A line from the sun is a helpful way to think about it!
You can see how your alignment is by sticking a three or four inch tall object to the panel, whatever shadow it casts is the side the panel needs to be tilted towards. Of course, unless you’re solar tracking east west is misalignment that can’t be helped, but for seasonal N-S it’s pretty useful. An empty soup can and a square of double stick tape is ok, sometimes the tape melts onto the hot glass, but it’s nothing a little acetone or a razor blade can’t clean up.