My old stove had a large recessed back to accommodate the gas line. The newer double oven freestanding 30" have flush backs except for the lower left side of the oven, there is a 10x10 recess opening to the gas connection. Does anyone know a reputable gas man in the Lake Elsinore area of Southern Calif ?

Have you checked with your gas company or propane company? Many such companies in the U.S. do this work or can offer names of certified companies/persons.
Specific recommendations for craftsmen or companies is not likely to be found on this site.

Often the company that sells the stove will have their own installers, might check with them. You can also have a local plumber do this work which normally requires a license.