I'm not sure where to start, because lighting food with flash can be as simple as it is inherently complicated.
IF you're proven comfort zone is using natural light, then learn how to use and optimise natural light to the best effect. Up till now, and in all honesty, you're at the 'starting stages' of building up your shots.
Don't look down on using natural light and not flash as a limitation. Some of the world's best photographers LOVE natural light, and a few will INSIST on working with nothing but natural light!
Since you were trying out using flash ... I'll share a little info with you.
Even with flash in a studio, what most togs set out to do is to RECREATE a HUGE light source - the sun.
Then they diffuse it - with diffusers that range from a few feet to several feet. Small diffusers or lightboxes like the portable 1 - 2 feet boxes are virtually useless. We're talking about lightboxes that are at least 4 or 6 feet or more. One of the foreign commercial photographers that I styled for likes to use a long diffuser that's about 12 - 18 feet long for his main flash. That's just ONE flash.
OK, so you have nice even diffusion and great light spread.
Now to have to CONTAIN and direct that light.
OK, with that start what you have is your MAIN light source.
You now have to start looking at FILL light.
Primary fill is usually global, and after you settle that, you need to look very very carefully at SPECIFIC FILL because shooting food is like shooting an ultra sharp, close-up of a very bumpy and very imperfect face. There will be loads of black holes, areas that are filled but too dark as well as protruding areas of different color, brightness as well as (and on to the next point) reflectivity.
Remember: By this point, you're still working with only TWO lights: a main, and a primary fill. Most togs will try their best to STOP adding lights at this point and start using reflectors. Adding lights at this juncture means adding an exponential level of difficulty in CONTROLLING the light.
With the use of water, oils etc to bring most food items 'to life!', you also have areas that will be as bad as mirrors! These will refelct too much light and blow out. These are controlled by BOTH light adjustments as well as tweaking the position of the food.
NOTE: When using flash for food photography, it is CRUCIAL that you can see the effect of all your set-up. This is something that's extremely difficult to do with speedlights. Not impossible if you are able to 'visualise' light with an extremely solid foundation in understanding the properties and behavior of light. The additional problem with using speedlights for food is that unless you're very creative and innovative, your choices of modifiers are usually very limited, and for those that exist, the range of control is limited.
By this stage, you have your BASIC two-light set-up.
Some will add lights, and many will start using reflectors, but ultimately the most basic and crucial objective is to CONTROL the light and use it to achieve a basic level of technical requirements.
Once you've mastered that, you move onto advanced stages of learning different and creative usage of light to achieve aesthetic or creative objectives beyond the basic technical levels.
It might be interesting to note that most working photographers do not usually have to stray very far from the basics.
Hope this helps shed some light on the use of flash in food photography.
Hmm ... I should start conducting Food Workshops! :bsmilie:
...:bsmilie:...
....:bigeyes: 
