This is a Remix of an design from sharanchius on Thingiverse to make printing easier/faster on larger machines. Everything fits on an Prusa MK3S, Creality Ender 3 or similar sized printer. Its very important you read the Printing Notes below!

Detailed writeup here:
Part 1: Introduction, hardware and assembly
Part 2: Setup, Software and Results
Part 3: Homeserver Edition with TrueNAS Core

Update:

Added an extended version which supports bigger coolers (Noctua NH-L9 for example) and regular ITX boards!

Changes:

• combined 43 parts down to just 11
• remade the frontpanel so a common powerbutton can be used
• removed most now unnecessary screwholes in combined parts
• fixed thousands of facette and mesh errors
• fixed a small clearance issue

Quick Specs (for more read below):

• supports ITX SoC (normal, 38mm cooler height)
  or ITX mainboards (extended, cooler 53mm height)
• 4x 3,5" drives natively, 2,5" with an adapter
• Flex ATX powersupply
• 120mm fan for cooling
• 2 front holes for dedicated Power / HDD LEDs

If you like it, consider a small DONATION :)

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Important Printing Notes

Print everything in PETG just to be safe, use PLA if you feel adventurous.
Use a 0,2 layerheight for the following parts:

• front_doors_combined
• drivecage_connector_combined

Everything else can be printed at an 0,3 layerheight to reduce printtime.
Some parts need minimal support, depending on the capability of your printer.

You do not need to print all parts, I made them modular to fit different sized printers:

If you cant fit side_left_combined on your bed, print the following parts:

• side_left_half-up
• side_left_half-down

Screw them together to make the part side_left_combined

If you cant fit side_right_combined on your bed, print the following parts:

• side_right_half-up
• side_right_half-down

Screw them together to make the part side_right_combined
If this part still doesnt fit on your printbed, continue reading below:

If you are using an Ender 3 or similar printer, by default many slicers only use 220x220mm of the bed, increase it to 235x235mm (the true bed size) in the slicer settings! You will also need to disable Brim, Skirt or Raft to make this fit!

Then use these files:

• optional-side_left_part1
• optional-side_left_part2
• optional-side_left_part3

instead of:

• side_left_half-up
• side_left_half-down

Screw them together to make the part side_left_combined

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Hardware / BoM

Disclaimer: AliExpress seems to region-lock many of the products now for some reasons. If you get an “Sorry, the page you requested can not be found”-Error, your country seems to be affected too. Found no solution yet

This is the board the original creator is using:
ASUS AT4NM10T-I – https://s.click.aliexpress.com/e/_9H6p2p
Intel Atom D425 - 1 Core / 2 Threads @ 1,80Ghz

And while it is very cheap, if you plan on using a Web-UI like OpenMediaVault and have decent performance while moving data, I recommend going with an more powerful board.
Here are some examples I found, but they are often out of stock:

ASRock QC5000-ITX -- https://s.click.aliexpress.com/e/_9iuz3z
AMD A4-5000 - 4 Cores / 4 Threads @ 1,50Ghz

ASUS HUMMING BIRD -- https://s.click.aliexpress.com/e/_AAi8Gp
Intel Atom D510 - 2 Cores / 4 Threads @ 1,66Ghz

Check your local retailers or eBay for similar boards too:
https://geizhals.eu/?cat=mbson&xf=4400_Mini-ITX

By default, there isnt room for most PCIe extensioncard!
Cards lower than the I/O ports are fine, wider cards might run into clearance issues with the drive bay legs.

If you want to use all 4 Bays, choose a board with 4 SATA Ports:
https://geizhals.eu/?cat=mbson&xf=2962_4~4400_Mini-ITX&asuch=&bpmin=&bpmax=&v=e&hloc=at&hloc=de&hloc=pl&hloc=uk&hloc=eu&plz=&dist=&mail=&sort=p&bl1_id=30#productlist

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Many M3x14 screws to bolt everything together:
https://s.click.aliexpress.com/e/_DFtP8AF

Two long M4 screws for the front doors.

You will also need 4 of these SATA/Molex combo cables, 40cm should be fine:
https://s.click.aliexpress.com/e/_9J0c7f

To power everything, you need an Flex-ATX / 1U PSU, for example:
FSP FSP270-60LE 270W - https://s.click.aliexpress.com/e/_98Zb4z

I would personally recommend going with an reputable brand and PSU, like an Seasonic Flex SUB 300W or similar - https://geizhals.eu/?cat=gehps&xf=4174_Flex-ATX

Since most PSUs has not enough Molex connectors, you also need adapters:
https://s.click.aliexpress.com/e/_9xo0gD
Check the cabeling of your chosen PSU for how many you need, for example 2 for the Seasonic Flex and FSP FSP270-60LE

Powerbutton (16mm Black or Silver, Power on (60cm)) used for front_panel_combined:
https://s.click.aliexpress.com/e/_A8AjVr

If you are feeling extra fancy, add some rubber pads on the underside:
https://s.click.aliexpress.com/e/_AsUIkZ

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Other things you will need:

• DDR2/ DDR3 / DDR4 SO-DIMM RAM
  depending on your CPU/board - check online
  go with at least 1x 4GB, buy 2x 4GB if possible
  
• 120mm PC Fan
  3-Pin or 4-Pin connector, depending on your board
  Arctic F12 are cheap, silent and available everywhere
  
• 12 magnets sized 5mm x 3mm
  https://s.click.aliexpress.com/e/_AkjWIH