The lower close fitting door with air inlet holes for the smoke box

Overall picture it is 6 '62 tall by 2 feet deep by 4 foot wide uses bricks and four paving slabs

This one shows the bits of concrete slab that make the smoke deflectors and gives a better front view .

This one may be on its side, but it shows how I cut the smoke hole in both slabs with an angle grinder .
TIP :-
Mark it and cut it out before you lay the slabs on the first stage , as it is much easier to do when it is lower down on a sand bed or trestles .
The top two roof slabs do have a mastic joint between them .... put in place on first slab and then the second was eased up to it to give a sound seal .
Adjustable racking a simple set of four uprights screwed to the corners . Long screws every 80 mm and some gash battening with six cheap wooden cut up broomsticks to make the shelves/racks

I'm going to try using an old steel bucket with a dozen or so 5 mm holes drilled in the bottom 10 mm up from the lower rim and then place a 20 mm hole in the side a few mm up from the bottom . This is so I can charge it with a large amount of sawdust and stick a simple £3.00 soldering iron in the big hole ( have it on a time clock for say three hours ) to get it smouldering.. it should run for 36 hrs or more if i get the air flow suitably restricted .
In the picture of the full frontal of the upper chamber you can just see one of the 10 mm smoke release holes in the base of the top course by the left corner.
i may need to make a couple of 20 mm holes in the top of the upper doors and use old wine corks etc to plug or unplug the holes to get a better through draught of nice cool smoke .
I've found that because the brickwork breathes it drops the day temp quite quick at night ( kept checking with an accurate digital thermometer) .
This has been a bonus on hot days , for as soon as the opened up at night internal temperature dropped to 50 oF I was able to get the smoker going . Leaving it going t overnight and then nip out at 07.00 ish to take the smoked stuff out before the temps got rising with the sun's arrival.
You do have to then let the goods dry off in the fridge as the moisture level has been ideal for the smoke particles to stick . I wrapped the food in some greaseproof paper and left it alone for 48 hrs . All the cheeses were lovely & dry but not too dry so was the smoked meats salt , salmon , various sausages , nuts , oils.
My next big step is to brine a leg of pork and smoke if for 3 days , then hang it in the meat drying safe to air dry for 15 months or so