According to the schematic, the terminals around R15 both go to VCC, meaning it should be bridged. But in the board layout file, one end of R15 goes to VCC (via C9, which also goes to the LM386 power), and the other end goes to the rest of the powered components.
Is one of the VCC points in the power section of the schematic a mistake, and maybe should have been TP5 - which is otherwise missing from the schematic?
VCC2: should power the preamp stage (the rest of the circuit)
R15 creates a low pass filter together with C9 and C10, this part is crucial to remove noise and make the circuit stable, otherwise, noise from the LM386 will go into the preamp and all will oscillate (R15 will stop this LM386 noise to go into the first stages).
The 1Wamp layout is critical, have a look at the layout images you can find in the article and also read the notes about that.
All the best for your project!, upload some pics when you finish it