The retired Scotland international admitted this was Woking's worst display of the season as they suffered their first defeat since New Year's Day, while Celtic collected their first league win since Boxing Day.
Gray said: "Farsley performed well but we let them dominate us in defence and attack. We sat back too deep and left too many spaces for them to play in.
To see a slideshow from the match, click here."I can see Farsley climbing out of trouble if they keep playing like that. We knew it wasn't going to be an easy place to come but we didn't perform anything like as well as we can."
Even before Craig Bentham finished off a splendid passing move in the 21st minute, to score the first of Celtic's three goals, John Deacey's team looked a class above Woking.
Rory Prendergast and Scott Gardner provided excellent service from the flanks and Andy Watson was similarly effective after leaving the bench in the 49th minute to replace the latter, who picked up a back injury.
Damien Reeves and Steve Torpey had been urged by Deacey to improve the side's goal output and they responded with one each. Reeves, whose strong running unsettled Woking's defence, was quick to react when Torpey's header was parried by keeper Ross Worner in the 38th minute.
Torpey's goal on the turn five minutes into the second half killed off Woking's hopes. Gray felt Marvin Morgan's disallowed goal just before the interval should have stood, but the striker was flagged offside, and Morgan claimed his shot had crossed the line a minute earlier.
There was no doubting Celtic's right to the points, however, and Deacey enthused: "We played well from first minute to the last.
"I have been harping on about the forwards not performing and not scoring but I thought Reeves and Torpey were excellent. That was the catalyst for the win.
"The first goal came from a great move involving four or five passes and when the ball was laid off to Craig Bentham he bent it round the keeper. It was good to see Damien and Steve score and David McNiven's arrival from Stafford Rangers brings extra competition for places."
McNiven's paperwork wasn't completed in time for him to make his debut but he is set to be named in the squad for Saturday's trip to Exeter.
Farsley Celtic: Aspden, Jackson, Iqbal, Santos, S McNiven, Gardner (Watson 49), Bentham, Krief, Prendergast, Reeves (Tuck 88), Torpey. Subs not used: Backhouse, Bambrook, Stamer.
Woking: Worner, Ruby (Sole 53), Lorraine, Hutchinson, Bunce, Batt, Gray, Pattison, Green (Lambu 53), Morgan, Norville. Subs not used: Gindre, Marum, Maledon.
Referee: R Joyce.
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