The excellent Battle Grounds sets from Miniature Scenery (if the link is still alive) were going out of production when I got hold of them about 2 years ago. The city grounds consist of 11 road tiles, 9 textured/city tiles and I also bought 5x 'blank' tiles that other terrain pieces can sit on. That amounts to a lot of terrain, and while they still aren't finished, I've made some progress over a long period of time when I feel like working on a big item (rather than minis).
Technically I was very late to the party - CNC Workshop was making these in about 2005 and I only saw them when they were switching to produce the New Paranoia boards. These older boards were made using a CNC router, so unlike the new laser cut boards, the cuts are rougher and less precise BUT the designs are a much better fit for gritty 40k environments than the cleaner modern design (which would be a better fit with Infinity).
My early progress photos have disappeared along with the mobile that they were taken on, but you get a decent idea from the shot above - each tile comes in parts on ~1-2 MDF sheets, which can then be stacked/glued to add depth. Rocks and coffee mixed with PVA fill in the bomb damage, and Dulux sandswept paint has been used to give the road portions texture.
When making each of the tiles, I'd sandwich the MDF pieces & glue between two thick pieces of MDF with some clamps and leave overnight. I think this is part of my slowness - turning out the unpainted product took quite some time alone.
25 tiles assembled and ~half painted with the base colours. I bought a few pots of dulux sample paint from Bunnings in the colours suggested by CNC workshop and they give a really good effect at a distance. The big caution - DON'T lay latex house paint on too thick or add coats without a lot of drying time. I have 3-4 boards in here that I rushed, and 12 months on they still get a bit 'tacky' when staking boards on top of each other.
Mucking around with a few pieces of scenery to see how the layout might work; a few unpainted concrete road barriers and MDF ruins, although still looks very sparse.
The blank tiles start to take on more of a texture using a sponge and lighter grey acrylic art paint. These probably need a few more washes or colours to add depth, but with the volume of boards to do, I think basic is probably enough. Grey being natural camouflage for my old grey knights... these are metal minis that possibly pre-date the internet.
Taking the painting further - I was always keen to try and add some road markings in a quick and (hopefully) easy way. The test board was not a great success for method - I cut slots in paper sheet and sponged on colour through the gap, but as some paint seeped underneath it wasn't very clean and the paper can't be reused straight away.
The base colour on 25 boards, with 1 'complete' road tile including markings.
Much quicker for mass production on markings was to invest $8 in a roll of Tamiya tape. This is great for laying out multiple boards before sponging, and with a razor can also be cut into thinner strips for the gutter edges.
Sponging on 2 different tones of yellow, and intentionally missing some patches gives a nice level of weathering while laying the markings down.
The corner tiles were somewhat more fiddly, particularly working around piles of rubble.
11 boards of road pretty much used up the roll of tape that I had - but was fun to do, and got me to a decent tabletop level of quality in pretty short time.
The pavement parts still need to be sponged with grey tones in this pic - the wonky yellow looks pretty good though with a bit of variation
Quick side job on one of the feature boards - the same masking tape used to apply black hazard stripes for detail.
All of the roads sponged with grey plus the yellow edge markings on...
...before maybe going a step too far and deciding to add some pedestrian crossings in addition to the lane marker dashes. These were done using some 8mm Tamiya tape - just alternating a tape-width on & off across the road. White paint has been sponged in varying degrees so that the markings aren't too sharp/stark.
The T-junctions also scored some stop-lines. Left-hand side of the road, ala Australian road rules of course :-)
Most of the boards still need some grey layers sponged onto the side areas, but they are definitely coming together. You could stick a painted army on these now and feel like they are in half-decent representation of a ruined city.
The board is massively configurable; it just lacks the 'hills' that were a staple of the green-flock generation of 40k terrain in the 90s. That part is still to go - after much haggling, I have a set of the CNC workshop city levels (also out of production) coming 2nd hand.
These are essentially 1-storey versions of the road tiles that will act as elevated platforms and block lines of sight. They are likely to take a bit of time to build, but once done I think that will finish off the 'board' work for the foreseeable future.