Design an undervoltage protection circuit for a simple powerpack based on 18650 Battery.

The Powerpack Module shall provide constant 5V DC based on a Lithium Ion 18650 rechargeable battery. The Battery is recharged with a module TP4056 being while being connected to 5V USB. The Powerpack Module includes an on/off Switch to disconnect the load before the Voltage Stepup (variable, based on Module MT3608 Dc-Dc Adjustable Step-up voltage regulartor Boost Voltage). The load is a LED with current draw of aprox. 400mA at 5V (2W). simple Schematics are attached. The project consists of designing a discrete circuit that disconnects the load of the connection with the voltage step up when the battery voltage drops below 3.6 V, acting as an undercharge protection and also to avoid flickering on the led while the switch is on but the 18650 battery is being drained. As an alternative you can also design a discrete voltage step up circuit for fixed voltage level (5V), and at the same time providing undercharge protection to the battery. In this case I can get rid of the MT3608. The discrete circuit should be able to be printed in PCB. Please do not use choose components that are exclusively available in SMD Format. The PCB Layout is not part of the project, but can be part of a later (new) project (you dont have to Design PCB Layout in this project). The circuit should be robust but it is designed currently only for Private applications (not for series production). I wil test the provided circuit with discrete components on a breadboard(Protoboard). The 5mm LED shown is just for showing purposes. We can have a separate Questions Session, which i can pay based on time (maybe to discuss using other similar components). Note: The same powerpack shall also be able to provide higher voltage for the load (i.e. 12V) when is being connected to other LEDs types. I am looking forward to a working Business relationship for similar projects.