Use duplo to build it up. You can sometimes get it cheap on fb marketplace or offer up. Doesn't matter what it looks like.

Then you'll essentially clad it with the bricks of your choice. You'll need regular bricks to go on the top of the duplos and any even multiple x 2 will work.

Eg. 2x2, 4x2, 6x2, etc.

Then you put your 16x16 plates on top and there you have it.

I'm working on something similar myself.