Letting tap water sit for 24 hours removes the chlorine, which inhibits fermentation.
Ideally, choose small cucumbers of a similar shape and size.
Fermentation results are more variable than those of any other food preparation method. They can be affected by the ratios of salt to water, brine to cucumbers, cucumber size, cucumber quality (freshness, growing conditions & weather, cultivar/variety, etc.), ambient temperatures during fermentation, and the mysterious behavior of lactobacilli. Past performance is no guarantee of future results. Pickles are fickle!
Try to keep the cukes immersed in the brine. Submerge, rotate or upend the top pickles daily, as needed.
If the pickles ferment too fast, refrigerate or add a little more kosher salt. If still not fermenting after a day or so, cut off a piece of submerged cuke and taste it. If too salty, add more plain water. (Salt slows and impedes fermentation.) Remove some brine to make room for the additional water. Allow 24 hours for the adjusted saltiness to equalize.