This Heart Filet Block 2 free crochet pattern by Belle Tracy is just one example of the endless possibilities to be found in the filet crochet genre.
The block above measures about 10 by 10.5 inches with 1 round of sc border.
Rather than making a lot of individual squares and then assembling them to form a blanket, one could conceivably do a foundation row that's long enough to allow for multiple "squares" to be worked contiguously, which would be a bit of a brain-bender in the beginning but would save a lot of work on the finishing end of the job.