Howdy, y'all. Here's a li'l ol' photoessay if'n you wanna build your own KROKlike object.
BYOB: Build Your Own Box.
A DIY feedback/true bypass box tutorial
What you gon' need:
A metal enclosure
A 3PDT stompswitch
A toggle switch
4 jacks, mono OK
A pot, pref 500k audio
Wire
Soldering iron
Solder
Patience
What you gon’ get:
1. A true bypass box. Bypass boxes are handy for a number of reasons: They can keep noisy pedals out of your signal chain; they allow you to turn on (or off) several effects at once; and they can essentially "add" an on/off stompswitch to effects that don't have one.
B. A feedback loop. A feedback loop takes the output of a pedal (or pedals) and sends it back to the input of that pedal (pedals), creating an unholy cacophony of noise. Put effects in the loop, turn the knobs, be amazed.
PART 1: The Switch
First thing I do is solder up the switch. After assembling a helluva lot of
these pedals, I've arrived at the process below as a fairly hassle-free way to hold the switch steady while soldering. While a third hand isn't required, it sure makes life easier for many projects. The clamp holds the switch better than the third hand alone, and makes it easier to manipulate.

Step 1. There are a couple of tricky connections to make on the switch — here's the first. Solder two wires (same color) to lug 9 of your switch, and connect the end of one to lug 4. Leave the other loose for now.

Step 2. Here's your other tricky connection. Pay attention now. You need to connect lugs 1, 2, and 5. I do this by stripping an inch or so off the wire I’m using, tinning it, bending it, and guiding it through all 3 lugs with needle nose pliers, then soldering. It takes patience, but it's totally doable.
NOTE: I’ve drawn on this photo in orange to better illustrate exactly where the wire goes.

Step 3. Go ahead and make the rest of the connections as shown in the next photo. The colors of the wire aren't important, with the exception the black wire on lug 7. This is ground, and it's always a good idea to use black for ground.

PART 2: The Case
Step 1. The next step is mounting the components in the case as shown in the next few pics. A pic of the top side of the case is included for reference.


Step 2. Here's a semi-tricky connection: the blue wire from lug 8 goes to the middle lug of the pot, and then the tip of the Send jack.
Step 3: Make the between the toggle and the pot. This is what turns your bypass box into a feedback loop. In this case, I’ve used an SPST toggle, so it’s easy. Connect the “on” lug of the toggle to the first lug of the pot.

Step 4. Make the remaining connections from the switch.
Here's a map for all the connections from the switch.
Switch lug 1/2/5 to tip of Out jack
Switch lug 3 to center lug of toggle switch.
Switch lug 6 to tip of RTRN jack.
Switch lug 7 to ground
Switch lug 8 to middle lug of pot.
Switch lug 9 to tip of In jack
The ground wire from lug 7 can go to the sleeve of ANY jack. The enclosure acts
as common ground for all jacks. In this pic, it's connected to the sleeve of the
Out jack. You can also see the orange wire from lugs 1/2/5 going to the tip of
the Out jack.
You’re done! Test that bad boy.