smax013, if you ever "publish" a tutorial on the steps for making such external HDs, immediately upon seeing it, I will bookmark it into my Chrome bookmarks.html!
There is no need really for a tutorial. The process is generally VERY easy. Most enclosures will come shipped with none of the screws installed, you can open up the enclosure right out of the box. You connect the internal SATA drive to the SATA port of the enclosure. For some enclosures, you then might use some screws to attach the internal drive to the "innards" of the enclosure (either through the holes in the side of internal drive or the bottom of the internal drive) to hold the internal drive in place...for others they might have some sort of "snap" piece that snaps into the screw holds of the internal drive. Then you usually put the cover of the enclosure back on (many of my drive, the cover slides over the "innards") and then put in several screws to hold the cover in place. Some might have a cover that snaps back on. Done.
There are variations. I have some desktop drive IcyDock enclosures that have a "tray" that you screw the internal drive to and then you slide that "tray" into the rest of the enclosure, which then locks into place and connects the internal drive to the SATA connection of the enclosure. There is then a level that allows you to release the "tray" and go a quick swap for another "tray" with a different drive.
They always come with instructions that are typically fairly clear.
If it helps, here is a link to a manual for one of the enclosures I use:https://eshop.macsales.com/tech_center/manuals/owcmanmepmu3am_r3w.pdf
You can see that the process to "build" the drive is to 1) remove two screws from the back of the enclosure; 2) slide the "innards" of the enclosure out of the case; 3) slide the internal drive into the "innards" such that internal drive connects to the SATA port of the "innards"; 4) use the provided screws to attach the internal drive to the "innards" from the bottom of the "innards"; 5) slide the cover back on; and 6) put the two screws you removed earlier back in. Done.
Most enclosures are very similar and just as easy, if not easier, to put an internal drive in.
Once the internal drive is installed in the enclosure, it is just a matter of connecting the drive to the computer and formatting the drive as internal drive rarely come formatted (and for me, even if they did, they are likely FAT32 formatted and I usually use NTFS with Windows and HFS+ with Macs, so I would be reformatting them anyway).