Carpentry and Woodworking - Table legs

I'm in the process of building a rustic kitchen table. I am using 4x4's for legs and sitting them on 2x4's that will lie flat on the ground and serve as feet. I am trying to figure out the best way to secure the 4x4's to the 2x4's that will provide the requisite strength but be invisible to the observer. This link (http://www.stoneycreekwoodworks.com/Furniture/Tables/dining.html) shows something similar to what I am trying to do.

The only thing I can think of would be to simply coutnersink several screws underneath the 2x4 up into the end of the 4x4 post.

Is there a better way to attach t hese two?

Mortise and tenon or dowels and glue are other options. I'd probably glue it and screw it, like you planned.

Ditto. Since there is virtually no sheer or twisting force on the feet, I would screw them with long course thread screws

Screws it is then. With respect to the glue would that be between the two flat surfaces then or glue the actual screws in place?

Pre-drill the 2X4's so that the shaft (not the head) of the screw will pass cleanly through it without catching.

apply glue to both flat surfaces according to the directions on the glue you're using.

Screw the pieces together. Since the screw passes through the 2X4 without catching, the head will draw the 2X4 & 4X4 together as the screw catches in the 4X4. Wipe off excess glue (squeezeout) and let dry according to the directions on the glue.

I'd use a screw at least 3-1/2" - probably a #10 or #12.