My maze solving abilities are unmatched, thus I naturally know what makes a good maze. First of all, the maze needs to be just as difficult regardless of the starting point. This is because almost all mazes are much easier to solve if you begin from the finish line. Next you should avoid short paths. They are pretty much just filler and won't confuse your challenger. You need to create multiple paths that take at least a minute to trace if you want to create a semi decent maze. My personal recommendation would be a path that splits off right after the start and cuts off right next to the finish line. This it'll appear like it should have been at least partially been correct since no maze would have such a long dead end. Thus your challenger will waste a lot of time thinking they're close to the solution. Now if you want to transform your semi decent maze in a great maze, you'll need to design each path as if it were it's own separate maze.

When you're creating a maze quality is important but can definitely be trumped by quant.i.ty. Thus if you've got the time, just expand the maze indefinitely.