Here’s a traditional Swedish farm accessory for gunk-laden soles. The dimensions are not critical, but be sure the edges of the slats are fairly sharp?they’re what makes the boot scraper work. Cut slats to length, then cut triangular openings on the side of a pair of 2x2s. A radial arm saw works well for this, but a table saw or band saw will also make the cut. Trim the 2x2s to length, predrill, and use galvanized screws to attach the slats from underneath. If you prefer a boot cleaner that has brushes, check out this clever project.
To inset the aprons 3/4" from the outer surface of the legs I made a spacer from 2 pieces of plywood.  This little jig made it easy to keep the distances uniform and also secure the apron to the leg while fastening.  Pic 3 illustrates how the jig, apron and leg are clamped together for fastening.  Each apron end is held by three 2 1/2" pocket screws.  The pocket holes were made using a Kreg pocket hole jig.  I assembled the short ends first and then the rest of the table base making sure the kerf (for clips) was along the top edge.  Since this is a long table I also added a cross piece in the middle of the table using pocket screws.