You forgot to add 0.1 uF decoupling capacitors on the power inputs of the ATmega328P.
Now, in the Arduino IDE the Programmer needs to be set as 'Arduion as ISP'
Typo: "Arduion"
Once this is done, one can treat the ATmega on the breadboard as a classic Arduino board.
This seems unnecessarily vague. Why not be specific and say: "one can treat the ATmega on the breadboard as an Arduino Uno."?
An external LED blink sketch is a good sketch to start with, or even an analog read/write sketch to test that the bootloader has been burned correctly.
I think it would be worth mentioning that the physical pins numbers on the ATmega328P used throughout the tutorial are not the Arduino pin numbers. Otherwise the reader is likely to have a bad time at this step when their LED is connected to PD7 but they're blinking PB5.