I would like to add some t-slots to my spoilboard. I know it's best to create the dado first (I have a 1/2" shank Rockler t-slot bit, so I have to anyway), so I'm comfortable with the idea of creating a 3/8" wide dado first.

But since the t portion is at the bottom of the channel (2nd operation), how do I program the t-slot, say if I want the t-slot at 1/2" depth below the top of the spoil board. I would like to start with the y line at x=3 (inches) and y=0.

I hesitate, because I am imagining, since this starts at the perimeter of the spoilboard, that the bit would start spinning, and the spinning t-slot will create a key-hole look at the beginning of the channel as it moves to the depth before it starts its y movement following the channel, and I want a clean look to the spoilboard.

Should I set the depth to measure from the "bottom of Z" versus from the top of Z in Aspire?

Can I just set the depth and location by manually jogging the spindle, then start it spinning outside the perimeter (x=3, y=0), and then Jog it through the end of the channel (x=3, y=24, Desktop MAX)?? i.e., can I use the jog functon of SB3 to cut?

My hand router is the Bosch Colt which only accepts 1/4" shank, otherwise I would have just used it freehand to run the t-slot bit after the dado was created.

I did not want to spoil my spoilboard. Thank you.