The 1uF capacitor that sets the frequency is charged though the leakage current passing through the LED. In ultrabright clear-case LEDs you see a faint emission in this phase (dark room implied). Then you are blinded by the following pulse :)
I also added a 1F 5.5V supercapacitor that keep the blinker running for more than 12 hours with a white LED. If a red LED is used, it lasts 24 hours.
If a solar panel is added in parallel to this circuit to top up the supercap during daylight (add a diode to prevent discharge back to the panel), basically it lasts forever.
The stand-by current is fractions of microamperes [uA] and the average lies around 30 uA (calculated). Not easy to measure, huh!
The hardest parts are to get straight wires and component leads and to keep everything in place when soldering when both your hands are needed to hold the iron and the solder. Then you need to make clean solder joints.
While is may seem a useless exercise, freeform electronics forces you to think out of the box even if you are reproducing someone else's work. Give it a try.
PS: working circuits impress 10x fold the audience.
