An illumination device generally comprises a plurality of light-emitting diodes (LEDs); a housing for receiving the plurality of LEDs; a light-diffusing member positioned adjacent the housing for receiving light emitted from the LEDs; and a slotted and reflective circuit board for operably connecting the LEDs to a power source and/or control system. The flexible substrate can be manipulated from a first, substantially flat position to a second position by folding the substrate along upper and lower longitudinal axes defined by slots oriented longitudinally and along either side of a central longitudinal axis of the substrate, such that the substrate can be inserted into the housing in an approximate U-shape. By manipulating the substrate from the first position to the second position in this manner, light from the LEDs that is not directly emitted into the light-diffusing member is collected and reflected by the circuit board into the light-diffusing member.