Hi, thanks for you interest. Normally, in a bathroom where the floor is exposed to a lot of moisture I would have not used a wood floor and I would have taken the wall tile down to a tile floor which would negate the need for a baseboard. But this was a powder room, and therefore has limited exposure to excess moisture. We used a painted wood 1x4 and "rabbeted" out a portion of the back about 1/2" to cover the tile; hence the baseboard stands out proud of the face of the tile by 1/4". Basically like these images I found online:

I hope this helps. Good Luck

Make sure you hold your tile high enough off the floor to allow the baseboard to set against the wall board and be nailed in to framing behind, and provide an expansion space between the bottom of the rabbet and the tile so that the wood can move as it needs to without putting stress on your wall tile.