How do I get Pencil Tool to stack blocks?

Blimey guys.  I don't believe what I am reading!

My canvas below is 2000 pixels wide.  I loaded the square brushes that come as standard, and set brush size to 50 pixels, and pushed out the spacing so that each touch down just overlapped the previous one.  By adjusting brush size and spacing, you can get the affect you are after, and work at any size.  I'd find it way to restricting to work on a tiny tiny canvas.

It's good that you started by turning on View > Grid, and View > Snap to Grid. The problem is that the Pencil is at 20 pixels.

The Pencil tool needs to be set the size to 1 pixel. You can choose any Foreground color, but I usually start with black for the outline of the shape.

Zoom in to make it easier to see the grid.

You could draw directly with the Pencil tool, but I find it easier to first draw a path with the Pen tool. As an example I've drawn a simple shape:

With the path selected, in the Paths panel, choose Stroke Path.

And choose the Pencil tool.

If you want to enlarge the image, choose Image > Image Size. It is important to choose Resample: Nearest Neighbor. In the screen capture below I'm enlarging to 400% which means that wherever there was just one pixel, there will be 4 pixels.

Hope this helps. If you have questions, let me know.

I think the only way to easily make Photoshop work that way is to make your canvas much smaller, and set your pencil size to one pixel.

The resulting file is very small, but you can Resample it up when you are finished using Nearest Neighbor (hard edges) to preserve the look.

You need to use a small file and a one pixel brush, or square brush.

PS brushes do not snap to grids or whatever. You have a wrong understanding here. Such stuff only affects transform operations. Other than that all PS brushes are antialiased and operate on relative fractional coordinates. PS simply doesn't work like you want it to.

Mylenium