Hmm... I've always had better luck chopping off the "pointy" ends, then halving the lemon (for stability) and cutting them into wedges, like you would for the kinds of lemon wedges you put in tea... (though I would slice them thinner than that, like 16ths instead of 8ths.)

Much easier to do it that way, because the lemon doesn't slide around, and it can be done with a paring knife.

Flavor won't be affected, though I generally use oranges because I like those a little better.