Poured sugar circle?

Yes, you can pour into an empty cake pan....any metal container works.

I used to use Pam spray and then wipe it out of the item, so there was a very thin layer of oil. You'd only need to spray the pan once and you could reuse it multiple times with-out any sticking. Make certain whatever spray you use doesn't contain any water.

Sometimes when using a cake pan like this, it is difficult to get the sugar/isomalt to release even after oiling the pan.  A couple simple techniques that might try...

1-Find a suitable sized rubber gasket at a plumbing or hardware store like Home Depot.  You can find gaskets in many sizes up to about 6 inches.

2- Roll out modeling clay on top of plastic food wrap (Saran Wrap or Sil-pat) with a rolling pin.  You can purchase modeling clay at any craft store.  Cut out the shape of your 'pond', you can be a little creative here instead of using a circle (from a gasket or cake pan).  Drape another layer of plastic food wrap on top of your clay. Your clay will now be sandwiched between plastic food wrap. The bottom layer of plastic food wrap is to keep the sugar/isomalt from sticking to your countertop.  Be careful not to burn your countertop, a marble pastry board works best. Let your sugar/isomalt cool a little (not boiling but still very pourable) and pour onto the cut out area.  After cooling, you'll be able to lift out the sugar/isomalt like a large piece of hard candy.
 

It's best to use parchment paper. It's sold on the same aisle as your foil and saran wrap at your grocery store.

Why not just pour it in a pool/ring on a silpat? http://cakeplay.com has some YouTube tutes and it seems like that's what they're doing. Check out the tutorials.

You don't need isomalt.  Use plain sugar and just enough water to help it melt, and cook it as fast as possible to the hard crack stage. Pour it onto parchment on a sturdy cake pan on a cooling rack.

You only need about a cup's worth of sugar to make a good sized pond. 

it's very pretty & that was a great save