I use Dieter's method. I drill two small inline holes where I want the line tie to be, take a piece of soft tempered SST wire and bend it into a tight U shape, slip the two wire ends through the holes in the lip, use a nail to keep the wire from getting too close to the lip, and then bend both ends down a 90 degrees, toward the bait. I've found that I don't even have to twist the "tag ends" if I just put a kink in them, just past the depth of the lip's length. I cut my lip slot, drill a channel under it for the wires, fill it all with D2T, and push the wired lip into the slot. The wires typically don't lay perfectly flat against the lip, and the spring tension from them helps to force the lip tight to the upper face of the slot, which is still flat and square to the bait.
If I'm making a bait with a longer lip, so there's more wire exposed, I wait for the bedding epoxy to set, and then I use some blue painter's tape to mask off a channel alongside the wires. This gives me a way to apply more D2T to make the longer wires rigid, and still keep the epoxy off the lips. I use my finger, dipped in denatured alcohol, to do the final shaping of the epoxy wire reinforcement.
I've made baits with the wires not epoxied to the lip afterwards, and they have never failed, but having them seated in epoxy makes tuning the line tie much easier.