Place the baguette slices on a sheet pan lined with parchment paper and toast in the oven until dark brown, 8 to 12 minutes.
Cool the baguette slices.
Meanwhile, line a half sheet pan with a nonstick rubber mat and place a 3-mm/.12-in-deep frame on top of the mat. Freeze this setup.
Place the baguette in a blender with the sugar and the water. Purée until smooth and uniform. Add the xanthan gum and shear for about 1 minute.
Pour this mixture into the frozen prepared frame.
Freeze to harden. Once it has hardened, remove the frame from the pan and flip the frame over. Peel off the nonstick rubber mat. Cut out ten 7.5-cm/3-in squares. Reserve frozen, well covered, until ready to assemble.