I probably should have posted the process but hes a quick break down. Dont know if this is the correct way of doing this but it seems to work for me.
1 -Identify the area and take measurements so it can be similar to the other side.
2 -mark out your design, try to plan out the steps so you arent remaking a panel because you put an indent on the wrong side.
3 -put the design into the panel using whatever tools you have a your disposal (hammer & dolly, bead roller, resip hammer, etc)
4 -remember you didnt account for the stretching that was going to take place and now you have to hammer and dolly your panel straight again. Some of this hammer and dolly work could have been eliminated if I calculated prestretch required
5 -using your patch panel as a template, scribe around the edges and begin cutting. I try to leave 0.125" from the scribe line and finish it with snips
6 -tack the edges
7 -begin welding. I like to use tig for this and I try to run a bead without stopping. It warps alot.
8 -hammer and dolly or use a planishing hammer to flatten out the welds, go over the entire welded area with a wide faced hammer/ slapper and try to finish the panel as best as you can.