What do you find is the best most simple method for silo

Imo the easiest way to build silos is with static html, because you have complete control over every aspect of a site, and unless you are good with code, it is nowhere near as simple with Wp as you need custom templates and/or menus and/or widget areas and/or sidebars, there are a lot of ways to create silos.

Assuming you are going with Wp, and this is just a suggestion, as you want quick and simple, you can construct a manual menu (using <a href links and anchor text) for each Category which you can then copy into each of the corresponding silo pages, that is the easiest way I know of.
With a bit of faffing you could style the menu as an unordered list with CSS to make the links appear horizontal.

I don't recommend this method if you are going to be constantly adding new content to the silos, as you will need to update all the links manually each time, but it's fine for one-and-done niche sites.

Another way is to use Posts/Pages as the main category and tag pages for the supporting content and the navigation, but this requires stripping the /tag base from the permalink structure, and possibly getting the tags to appear at the top, rather than the bottom.
It does make adding nav links a whole lot quicker though.
If using a SEO plugin with this make sure it does not add the noindex metatag to the Wp tag pages.

Just remember it is the internal linking structures of pages that form a silo, the content can be anywhere on a site.