The guidelines for producing counting blocks in braille are as follows:
1. For kindergarten through grade 3 counting blocks should be shown as a tactile graphic. Blocks should be no smaller than 3/8 inch square. Groups of blocks should be grouped the same as they are in print with 1/8 to 1/4 inch between individual blocks, and 3/4 inch between groups of blocks.
(When it is necessary to use more than one braille page to depict the counting blocks, a transcriber's note should be inserted before the start of the tactile graphic, telling the reader how many pages the tactile graphic involves.)
2. For grades 4 and up counting items can be represented by using the letters "on" for one, "tn" for ten, "hn" for hundreds, "th" (uncontracted) for thousands. A transcriber's note must be added explaining the use of braille symbols as a representation of the print object.
Yes, they do require quite a bit of time to produce and space in the braille volume. This is perhaps not the answer you were hoping for, but it is considered the best practise for the grade 2 level.