I used an angle grinder with a thin blade to grind through the welds and then a hammer to tap the old window guard into two halves.
Step 2: Work on a table
Careful craftsmen will work on a table and not on the ground.
Step 3: Weld in a base
Weld a reinforcement frame to the part that will be the base . Also weld in a grating of some kind. I used something called "horse panel" that is available at farm and ranch type supply stores like TSC.
Step 4: Add Lower brackets as needed
Weld on some substantial lower brackets. A simple straight rod will do.
I make scrolls so I made these of 1/2" solid iron square bar. You can see some of my work at http://ironandwood.com.
As WallE said, "tadaaa." The person I made this for was going to have it sandblasted and painted so I just threw on some canned spray paint to preserve it while it waited.