Preheat oven to 325 degrees.
Grease or butter a large sheet pan. Set aside.
Spread almonds on a large rimmed baking sheet, and toast on middle rack of oven 8 to 10 minutes or until fragrant, stirring 2 or 3 times.
Remove from oven, and set aside.
Meanwhile, combine water and sugar in a 4 quart saucepan, and cook over medium-low heat to dissolve sugar completely, stirring occasionally, about 6 to 7 minutes.
Use a pastry brush dipped in water or cover with a tight fitting lid for 3 to 4 minutes to wash down crystals from sides of pan.
Increase heat to medium and continue cooking, swirling pan occasionally, until the sugar has taken on an amber color, about 15 minutes more.
Remove from heat and add warm almonds, tossing gently to evenly coat the nuts.
Pour mixture onto prepared sheet, scraping pan as little as possible.
Rub half a cut lemon over the confection to flatten it.
Cut into diamond shapes while still warm or cool completely, and break into shards.
Store in airtight container at room temperature.