I'm so happy you asked this question!! I've never made a bowl or basket and have one I put on my Brother card today to give it a try.
Thanks for asking what I was embarrassed to ask! :-)
*4U
Iva, I do believe this becomes one of those - that is the preference of the one making the bowl - most times - the only way you can tell the difference in a FSL item - is the direction of the design - as you use the same thread in the top and the bobbin. The great thing about a bowl is - if you don't like the way it looks - just flip it around - you will have the otherside of it in a second. Keep on stitching.
Definitely on the outside. However, if you wind a bobbin with the same colour as the one being sewn in the design, the inside and outside of the bowl look very similar. Hope this helps.