Using watercolor blocks
The glue might prevent this (depending on if the glue really is spread perfectly along all the edges), but a visual inspection should be enough. More likely is that the surface tension of the water will keep it from spilling over the edge.

If you are really worried about this and your technique requires huge amounts of water on the surface of the paper, you could apply some removable liquid frisket to the edges (available online or at your art supply store [e.g. windsor&amp;newton]). Test it to make sure that the brand you are using does not damage the surface of the paper when you remove it.