Over the weekend I prepared a new flower bed by turning the soil and mixing in a bag of compost. The soil is pretty good; nice & black, not too much silt or clay. A good black moist soil. However, once I raked the bed out flat and observed the drainage, I noticed certain areas just do not drain at all and the water just puddles. There is a fair amount of natural rock and some gravel that I tilled in, but I'm not sure what else I can do to improve the drainage in the bed. Any suggestions on how I can correct this? Should I add more soil or compost, or rocks/gravel?