Stumpy,
This link:
http://www.clay-king.com/kilns/kiln_accessories/kiln_brick_and_kaowool_blanket.html
shows the right ceramic blanket. 4.08 square foot, two square foot
minimum. Two square feet would be more than enough. Any pottery
supplier should have this stuff or its equivalent. Be aware that this
stuff does shed fibers that, like fiberglass and rock wool, are bad to
breath. When I use mine I wear a mask and gloves. Just a cheapie
disposable mask. If handled with a little care the stuff is easy to
re-use. I keep mine in a plastic garbage bag. When I need to make a
little oven lots of the time I can get away with laying the stuff on
the welding table, laying the part on the kaowool, and forming the
kaowool around the part, leaving the top open enough to apply the
heat. The part you are going to solder may be small enough that you
can just lay it on an insulating surface and go to town. I have found
that Hardi Backer Board, made for wet locations like showers and for
hot locations like around a fireplace insert in new construction,
makes an excellent silver soldering pad. I had some left over from
when my house was built. I don't mean greenboard. I wonder if your
home improvement center might have a damaged sheet they would sell for
cheap.
Eric