The board designer intended for you to install parts on the other side of the board. I've built Quarantine boards both ways. You have to take into account that the components are mirrored when you install parts on the "wrong" side. This includes the pots. The VOL & SUST pots will be swapped and all three pots will have their rotation backwards. The easiest way to correct the pot rotation is to cut off the two outer legs and wired them to the opposite pads with jumper wires. Their positions will still be swapped, but that's no big deal. The transistors will be backwards unless you deliberately reverse them. Installing them backwards won't damage anything, just turn the trannies around and see if that fixes it.
The other thing to keep in mind is that it is very easy to install a part in the wrong place because the assembly diagram in the build docs is drawn for installing parts on the other side. I have made that mistake more than once, but caught it in inspection. You will need to carefully inspect every part to make sure it is in the right place and oriented correctly. A quick glance tells me you got all of the capacitors in the right place.
The flat part faces away from the pots on the silkscreen. Is it supposed to face the other way in the back? I thought I was wrapping my head around it, but maybe not.
