To "trigger" the walking, just add the function after your mining procedure 
Simba Code:
begin
SetUpSRL;
ActivateClient;
DeclarePlayers;
LoginPlayer;
repeat
MineRock;
Bank;
until(false);
end.
You can do that because your procedure repeats the mining until a full invo. If it didn't you'd add another repeat in the above for MineRock; until(InvFull).
I would highly suggest having a better function for finding the clay. Try using TPAs?
Simba Code:
Function FindObj(Hue, Sat: Extended; Color, Tol, w, h: Integer; ObjText: string): Boolean;
var
CTS, I, N: Integer;
TPA: TPointArray;
ATPA: Array of TPointArray;
begin
CTS := GetColorToleranceSpeed;
ColorToleranceSpeed(2);
SetColorSpeed2Modifiers(Hue, Sat);
For N := 0 to 1 do
if not FindColorsSpiralTolerance(MSCX, MSCY, TPA, Color, MSX1, MSY1, MSX2, MSY2, Tol) then
Exit;
ColorToleranceSpeed(CTS);
ATPA := TPAToATPAEx(TPA, w, h);
For I := 0 to High(ATPA) do
begin
MiddleTPAEx(ATPA[i], x, y);
MMouse(x, y, 0, 0);
Wait(50+random(10));
If IsUpText(ObjText) then
begin
Result := True
Writeln('Found Object');
Break;
end;
end;
end;
That's something I always use 
Now where are you going to be mining? If in walking distance to a bank, just use a path creator (I can't find the one I use, it's different but I believe they all work the same) and make a path. If it's far from a bank, make sure to have teleporting between the walking (Teleport, walk to bank, teleport, walk to mine, etc.) those will require functions as well.
If you'd rather keep it simple simba's minimap obj detection is pretty accurate so you could always use symbols like mines, water sources, shops, banks, etc. and have your mouse adjust itself based on their positions. But if you'd rather just use SPS then ignore this portion 
Where are you planning on mining the clay exactly?