What's a shaping rack?

So after seeing the shape on the blank I get super excited. Now I want to cut it out and get the planer out. But what should I cut it on? I thought that leaning it on a workbench might not be best for the soft foam, so after a bit of reading on the net, I worked out I need to make some shaping racks. I found some good plans here for a temporary set of stands and set off to the timber yard.

I bought the following:
2 buckets
a bag of cement (quick set)
3 lengths at 2400mm of 2x4" structural pine
1 length at 1200mm of 1x4" dressed pine
4 x L brackets & screws
Some wood glue
and I salvaged some wood screws from my shed.

I finished assembling the stands in about 2 hours.

I then stapled on some carpet underlay on the flat ends and then glued (with Nail Bond cement) strips of carpet to make a sway to hold the board on it's edge. Here's a completed pic of the stands: