This is not a good idea for an actual water filter, a prefilter maybe, but not an effective pathogen filter.
It is an attempt at making a ceramic filter from gathered materials in the field. There is no way to determine the pore size, some could be tiny, others large. A ceramic filter must have consistent pore size, such that it can filter out pathogens with at least a 99.99 % accuracy, as tested in a lab. The doulton ceramic filters are an example of ceramic filters that are tested to work consistently.
https://doulton.com/product-category/ceramic-filter-candles/
Attempting to replicate this technology with a handful of clay and cow crap is a very good way to get sick.