I’ve made a knock-down base held by a half-lap joint, topping the legs with square tenons.  The top is square and the stretchers are at 90 degrees.  How do I best locate and cut the mortises for the through 1 inch tenons?  If I drill and chisel from below, I risk tear-out and poor fit from above.  Should I invert the base, and go from the top?  Thanks.  John