Preheat your oven to 180°C.
Grease and line a 26 x 8 cm (10¼ x 3¼ in) bar/loaf tin, leaving overhanging baking paper on the two long edges. This makes it easier to remove once cooked.
Beat the egg whites with an electric mixer until soft peaks form.
Add the caster sugar with mixer running, a little at a time, ensuring you beat well in-between additions. Continue beating until all the sugar is dissolved and the mixture is stiff and glossy.
Carefully fold in the flour and almonds and then tip into the prepared tin and smooth the top with a spatula.
Bake for 30 minutes, or until just firm.
Remove from the tin and place on a wire rack to cool completely. Wrap in aluminium foil and set aside overnight.
The next day, preheat the oven to 150°C (300°F) and line two oven trays with baking paper.
Unwrap the almond bread and use a sharp serrated knife to cut into wafer-thin slices.
Place onto the oven trays, cut side up, and cook for 25 minutes, rotating them halfway, or until dry.
Allow to cool on a wire rack before storing in sealed containers for up to 3 months.
