flashing leds

I have an assignment to create a circuit without a 555 timer or an op amp which flashes an LED at 2Hz for 5 seconds then stops it. Ive created the timer part using an RC circuit however im not sure how to implement the flashing part. I have made other circuits which flash at 2Hz but dont stop...

Found this simple circuit on youtube and I'd like to know the equation for how to vary R and C to change the flashing frequency. Also, how to increase the current through the led with 3.3 V battery as power source to maximize brightness.