How to actually create a theme?

Windowblinds with Skinstudio I S  The only way to go.   

What neone6 said, Windowblinds 10 and SkinStudio 10, and if you are using Windows 10, I would recommend Start 10 too. None of these hack your system files either.

Ok thanks both for the answer!

@LightStar, about the start bar, as i said, i prefer using Classic Shell, since it allows more manipulation. As an article sais:

For example, in Classic Shell I can drag and drop a program, moving it from one folder to another. Start10 doesn’t have that ability. In Classic Shell, I can right-click on a folder and create a new folder. Start10 can’t do that, either.

More than anything, in Classic Shell I can move a program from, say, the bottom of a folder’s list to the top -- very important with Word in the Microsoft Office folder, for example, which deserves to be near the top of the folder, instead of squirreled away at the bottom. In Start10, you can’t reorder items by drag and drop.

and i feel really comfortable with Classic Shell's way to do.

Yes, but Classic Shell hacks system files if I remember correctly. Also, using Windowblinds and Classic Shell together is something I would not recommend. I don't think they will work well together at all.

Nothing wrong with system files changes IF the uninstaller can recover them, and classic shell uninstaller can do that.

Btw a little note: in my main post i said "free software"...

If you wish to create a theme such as the one you linked then you must purchase the software that allows you to make it.

There is no FREE software anywhere to create themes. 

Classic Shell does not hack any system files. I don't know where you got this misinformation. I suspect you work for Stardock and are trying to spread misinformation about Classic Shell on purpose?

He was just misinformed,please put your paranoid elsewhere.   

No, I do not work for Stardock, and I did say "if I remember correctly", which if I did not I apologize. But I don't think it will work correctly with Windowblinds installed. Is there anyone out there that has tried?

Well i was trying to find out if there's any other free alternative. You said "you must purchase THE software that allows you to" as if it was the only chance. It would be so if said customization was forbidden by the os and Microsoft forced you use one specific program to do so. 

But since it's a third party software doing something allowed by the system, that means there's no limit to other companies/open source developers making something equal.

In theory there can be others...in reality there aren't.  Back at the origins of Windowblinds there were 3 others...all now gone.... as Windows [the OS] became harder to work with at the GUI level the others could not afford the development cost/effort and expired.  Win 7/8/10 is not Win98.

One alternative left is a reverse-engineered [hack] of the default Windows GUI coding which, if Microsoft ever felt the urge could be squashed permanently as it is in violation of their EULA.

So....when push comes to shove 'The Program' to do it is Windowblinds.

What I said was .... If you want to make a theme like the one you linked https://www.wincustomize.com/explore/windowblinds/7777/ then you need the software that was used to make it which is SkinStudio - https://www.stardock.com/products/skinstudio/ and themes made in SkinStudio need WindowBlinds installed to run the theme.

SkinStudio is free with the purchase of WindowBlinds - https://www.stardock.com/products/windowblinds/ 

There are no other companies/open source developers making something equal to what you asked for in your post.

Moreover, SkinStudio will require you to use a graphics program like Photoshop or Paintshop in conjunction with it where you will create the graphics, size them, etc.

I could not waste any time with this guy who apparently has no desire to make a purchase whatsoever,  .

Quoting Gaspershooters,

reply 16

I could not waste any time with this guy who apparently has no desire to make purchase whatsoever,  .

And quoting DaveBax, reply 17 ->

Oh, leave the poor guy alone.  He obviously is as poor as me. When Social Security pays me only $500.00 a month and I am retired, disabled, and my rent is $800.00 a month, every penny counts.  Every month is a new adventure and life is beautiful all the time, and they're coming to take me away ho ho, he he, ha ha, to the funny farm....

Don't forget to double load your IRAs, 401Ks, Roth...s, etc, etc.

Necrothread strikes again!