Attempting to make a Buck/Boost Converter (Flyback) with a 555 timer

[ketszim]

So I've managed to make the following buck/boost converter using an ATTINY85 to generate the square wave, but I wanted to try and make this same circuit with a 555 timer to generate the pwm, would this be possible? And what are the likely issues I might run into?

The circuit I built: https://easyeda.com/GreatScott/ATtiny_Buck_Boost_Converter-RXig0YIif
Credit to GreatScott: http://www.instructables.com/id/DIY-BuckBoost-Converter-Flyback/

This is the idea for the 555 timer circuit(This is the closest thing I could find to my idea): http://www.555-timer-circuits.com/led-dimmer.html

Thanks!