This technique is also known mostly as "snowballing", or, occasionally, connector blocks.
Unfortunately, what most authors don't tell you is that after sewing and then pressing the "snowball" to the corner, you should NOT cut off the back layer of fabric, the corner of the base square. Only the middle layer should be trimmed out.
IF you will leave the back layer on, any discrepancy where the snowball is not exactly matching to the corner is fine as long as it's enough to catch within the seam allowance of joining to the next block.
AND, leaving the corner of the base square on will make it easier to match the next block to it because the base block was square to begin with.
If you are planning to handquilt the quilt, then you may want to rethink not trimming the extra fabric because 2 layers may be harder to quilt.
Jan in VA