throw-in spot
 

A1 in-bounds the ball from baseline. A2 catches the in-bound pass near the half court sideline, but has 1 foot in & 1 foot out (both feet on floor).
Where is the ball to be in-bounded next by team B?

Thanks

This is a floor violation, so at the spot where the ball was caught.

2007-08 NFHS Basketball Interpretations
SITUATION 3: During an alternating-possession throw-in for Team A, thrower A1 passes the ball directly on the court where it contacts (a) A2 or (b) B2, while he/she is standing on a boundary line. RULING: Out-of-bounds violation on (a) A2; (b) B2. The player was touched by the ball while out of bounds, thereby ending the throw-in. The alternating-possession arrow is reversed and pointed toward Team B's basket when the throw-in ends (when A2/B2 is touched by the ball). A throw-in is awarded at a spot nearest the out-of-bounds violation for (a) Team B; (b) Team A. (4-42-5; 6-4-4; 9-2-2; 9-3-2)

Correct. If the throw-in is untouched and goes out, that's not an OOB violation, but rather a throw-in violation, and hence why in that situation you'd bring the ball back to the spot of the original throw-in.

The subtle difference between the two situations is probably why the OP posed the question. Hopefully this helps. Navadaref's interpretation is spot-on for the OP situation.