What they said. 1/8" is just too thin. You can glue it to the tooling plate underneath and it will be held over its entire surface. I'm not too comfortable using only the glue, although many do, but it sure helps.
You can use hot melt, super glue, or even Loctite with metal. All work pretty well and will release with heat.
Not knowing what your part looks like, it's hard to suggest further steps. For example, if you have some holes, it can be helpful to drill these first and then use them as hold downs as well.
Cheers,
BW