The most important thing is to not overfill the filter basket, because when water comes up through the stem/tube and spreads over the grounds, it takes up space in the filter basket as well. So, if you fill the filter basket to the brim, when water goes in, the grounds flow out. If you need to put lots of grounds into the filter basket, you can consider using a spring underneath the filter basket to press the basket and spreader against the lid, which is the design of the Farberware Yosemite Percolator. But you do need a tight-fitting lid for this. Alternatively, you can use stainless steel binder clips to hold the spreader tight against the filter basket.