Blue fixturing wax application

Attempting to use blue fixture wax to secure .125" 6061 AL to a sacrificial piece for machining. I have avoided using it until now because I have issues with my stock being level. Last time I attempted use I heated the wax, placed the stock over the heated wax, applied pressure with an arbor press and continued to heat.

Each time I use it, the end result is the same. There is a gap between the stock and the sacrificial piece. This has caused my depth to be off in areas which has resulted in broken .063" mills. I may continue to avoid this stuff. Everyone else only seems to complain about removal, which I do not think is bad at all.

So, what do I need to change in how I am going about using this stuff?

I got it guys. I used a bit less, but I used it directly on the MDF waste board. I think the .500" AL stock was acting as a large heat sink and causing issues.