Routing a big irregular inlay
Hello, everyone; I'm completely new here, but it looks like y'all are the sort of folks I'd like to run this project by.
Is there a clever way to copy the exact contours of a shallow opening, to create an inlay of plywood to fill the gap? All the inlay advice I see is for small-scale kits where you're cutting both the opening and the inlay from scratch; but I'm looking to fill an irregular opening in a tile floor. See attached photos for scale and examples of the edge. I'm looking to create a piece of plywood to precisely cover the grey concrete, the surface of which is about 3/4" lower than the orange tile.
My husband and I just had a plumbing nightmare descend on our house that required trenches to be dug in winding pathways throughout our ground floor. The excavators replace the dirt and the concrete, but not the flooring; that's our job to have done once we see whether or not we're getting any insurance money.
For various reasons, we're not ready to do the complete reflooring quite yet, and want to lay some temporary filler in to replace the tile's thickness, which is between 3/4 and 1 inch and constitutes a significant tripping hazard. I'm mainly a theatrical carpenter, so my first instinct is to fill the gaps with 1/2" or 3/4" plywood topped with 1/4" hardboard (Masonite).
And back to the question:
The only thing I can think of would be to lay the sheet of wood over the edge to be matched, and use a flush-trim bit to cut blindly through the sheet along the path of the tile's "cliff". But of course that would give me the exact opposite of what I want. I could keep the "offcut" instead of what would normally be the main piece, but the contour would be wrong on the deeper irregularities. And then the even trickier part would be doing the same thing on the other side of the piece and allowing for the right amount of kerf.
Does anyone have a better idea? I am by no means a router expert; I'm a fairly experienced user of power tools in general, but mostly for large chunky theatrical projects rather than cabinetry. Fortunately, I have more router than I deserve -- a 1 1/2 HP, 1/2" collet Porter-Cable plunge-capable router that was my dad's.
Thanks for any thoughts you would like to share!