Today I made a block with one of these, so I though I would share how I deal with cutting at this size.
This block is in honor of the Kentucky Derby and I call it May Roses. For some of the units in this block you need to cut two squares, one red and one green that measure 5 and 3/16 inches square to cut into four triangle units.
The first thing to realize is that 3/16 of an inch is just slightly smaller than 1/4 of an inch. My first cut is to remove a square of my fabric from the main piece that is just a bit larger than this:
Here is the finished block:
You can download the free pattern for this block all month long from my Craftsy Pattern Shop -