How can I make a floor like in Mario maker?

Hello everyone!!! I would like to know how I can make a floor like Mario maker, which changes automatically when it detects that there is another block of soil next to it.

And also, can it be done with a tilemap?

Thank you!!!

https://www.dropbox.com/s/wyiz1r06s2p3o ... e.c3p?dl=0

ref tutorial: http://i.imgur.com/XMyUpzN.png (the original website that had this article went down, but someone saved it as an image)

My example is made in C3, but it can be done with just one event so you can use the free trial to play around with it.

Thanks!!!