We have some 5 layer maple pinblock (P/B) stock made a while ago. Steinway L P/B is small. So pick a smaller size stock, save the large ones for other pianos. First, trace the bevel side line on to new stock where it butts against plate flange. Adjust bandsaw blade angle to match the old P/B, cut new P/B, skip the divot part.
Cut the divot part with a jigsaw, blade angle matching the old block. Check on plate.
Brush graphite on plate webbing area, put P/B on, and press/hammer everywhere. At the spot where the plate contacts the P/B, there will be black marks. This is the high spot on new P/B, needs to be sanded off to lower it. Repeat this fit and sand process till marks are everywhere on the P/B.
Trace a line where the wood is contacting the plate, mix epoxy with filler till a consistency of mayo, pour under that pencil line, clamp onto plate.
Clean up epoxy squeeze out, let dry till the next day.
On the next day, sand off excessive epoxy, clamp P/B to plate again to check if there is a gap anywhere. Mark for tuning pins.
After drilling for tuing pin holes, mill the new P/B to match the old one
When chopping the new P/B for length, leave a little room for it to shift left to right in piano to adjust itself. Double check plate height, then done.