I wasn't going to say anything, but that's how I did the MD 3XL OP in the Gallery. The 3XL and the Flippin' Stick, the same. That'll have to be my method 'til I get Hand Pouring down. It works well, but You HAVE TO keep Injector Pressure on it as it cools since You don't have the Sprue and Runner to feed the cooling/shrinking. It does work, but not nearly as well as an Injection Mold, of course.
For the 2" wide OP Molds, I use a 1/8" thick piece of 2" wide Aluminum Flat Bar. Cut it to length with a little "overhang" on each end of the OP mold, drill the hole(s) at the "head end" of the cavity so it lines-up with the end of the cavity, round-off all edges.