Well, if you check back to THIS POST you can see the kind of thing that I made back in 2014, but I've gone on to build tiles of all kinds of different shapes and sizes since then ...and if it turns out that they don't join up properly when I'm designing an encounter, I just make an additional piece that fills any gaps ;) (as that's the beauty of this system - the tiles are so quick and easy to build that you can do something like that in a few minutes).
However, if you're looking to build a modular base set to get you started (or to expand upon the stuff you've already built) then I've had a bit of a rethink - and gone ahead and added a second page of the floor texture to the original download ...just to make something like this a little easier.
And, as you can see, this new version has a ½" tile around the edges ...as this will cut down on wastage when you follow this particular method.
Anyway, on with the tutorial...
OK then, in the picture above I've illustrated how you can cut up eight different sheets to get the most out of each printout (note that some of them are the same except for the fact that they have been rotated - and this is so that the texture appears different on tiles of the same shape ...the corner passages for example).
So, once you've got those glued to some cardboard (or foamcore, etc.) and cut out as shown above, the next thing you'll need to do is add the walls to the areas I've shown in the diagram below.
And, as you can see, this should provide you with a good number of rooms and passages to get you started, and allow you to build a few basic dungeons ...like the one pictured below.
From here you can expand on your tile set in whatever way you like ...maybe adding a few smaller 4x4 rooms, or even gluing a couple of the original floor textures together to make a huge chamber ...the choices are endless :)
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Anyway, I hope this was a useful article for anyone interested in this kind of thing, and I'd also like to point out that all of the textures I've made thus far can be found over on THIS PAGE (on DriveThruRPG ...they're PWYW - so grab 'em for free, or pay as much/little as you like).