DIY variable bench power supply (For actually 17$)

How to build a variable bench power supply, capable of outputting 6A 24V.

I am buying most of my tools and components from AliExpress, if you are a new user, download the Aliexpress app and subscribe using the following link to earn 5$.
https://a.aliexpress.com/_mtN5u3w

My Build:
-Binding posts: https://ebay.to/2JlUvaT
or aliexpress: http://s.click.aliexpress.com/e/IAaA6IE
-Voltmeter Ammeter: http://ebay.to/2jZs7mB
or aliexpress: http://s.click.aliexpress.com/e/r3zBYr3
-12A buck converter: https://ebay.to/2RBuIy4
or aliexpress: http://s.click.aliexpress.com/e/vFAqFAM
-Power supply: http://ebay.to/2GIVAXZ
or aliexpress: http://s.click.aliexpress.com/e/jmQJqbE
-3A buck conveter: http://ebay.to/2i4euC0
or aliexpress: http://s.click.aliexpress.com/e/IuzNvvZ
-Wirewound potentiometers: http://ebay.to/2jkUec4
or aliexpress: http://s.click.aliexpress.com/e/zNnIeaA
-Knobs: https://ebay.to/2XuitKP
or aliexpress: http://s.click.aliexpress.com/e/IyfMbAq
-Switch: http://ebay.to/2A6iyc3
or aliexpress: https://s.click.aliexpress.com/e/_d7evFeP
-Socket: http://ebay.to/2BkdsGJ
or aliexpress: https://s.click.aliexpress.com/e/_dVW3yl3

Cheaper build (17$) (with cheaper binding posts, potentiometers and knobs):
-Binding posts: http://ebay.to/2zE39Ab
or aliexpress: http://s.click.aliexpress.com/e/EmEyrrf
-Potentiometers with knobs: http://ebay.to/2GIVJL1
or aliexpress: http://s.click.aliexpress.com/e/2n2vrBa

Additional things:
-Enclosure BOX (12*19*8 cm): https://ebay.to/30VZpoG
or https://s.click.aliexpress.com/e/_dWISbkz
-150PCS Heat Shrink: https://ebay.to/31MN4Tg
or aliexpress: http://s.click.aliexpress.com/e/mem2jqV
-Power Supply Cable: https://ebay.to/2X1fmLc