Which is the best layout technique for builduing the mobile version of my website?

Hi Jamie :)

For me it is about content to be displayed on the page but there is nothing quite as easy as a well structured grid system to get you moving.

It is the layout within the rows and columns of the grid you can then start to code around with.

I wouldn't recommend coding a full site using flexbox just yet as there is not still full support un-prefixed, however I use flexbox for individual section of sites for its vertical centering properties and fluid alignment. More Info Here

To recommend something to get you going and understanding more of the options which you can then begin to code on your own I would say take a look at a framework like Bootstrap or Foundation, they have extensive grids you can work with and tons of cool features you will learn to code on your own and enjoy the speed at which these can let you work.

As with most things web design and development there is no true answer as it is mainly down to what suits you and your project the best but a grid at the moment is a solid place to start.

Hope this helps :)

Craig