Underwood continued: "I thought we were excellent again today. After the first few minutes when they put us under a bit of pressure, I thought we looked very, very good going forward and played some good football. We managed the game very well."
Slough's opening goal on eight minutes set the Rebels up for what turned out to be a comfortable win - the club's eighth in a row in all competitions - but it came after a good opening few minutes from the visitors.
Robbie Parker was inches away from getting a touch to a dangerous cross from out wide on the left. But the Rebels were soon into their stride, and in-form right winger Warren Harris was on hand to convert a Gavin James cross at the back post, with Lucas Perry unable to clear on the line, with eight minutes played.
Slough took control of the game; James almost capitalised on a defensive slip but his effort from outside the box was easily held by Ian Brown, and then Mark Nisbet narrowly missed his header from James Dobson's near post corner, with James unable to get the ball out from under his feet to shoot. But the threat from Biggleswade was still evident and Craig Daniel sent a free header wide of the post from a long flighted free kick.
A second Slough goal was certainly on the cards, and duly arrived on 33 minutes courtesy of Lee Barney's quick reactions. Waders defenders backed off Simon Dunn, who unleashed a thunderbolt from 20 yards which Ian Brown did well to tip onto the underside of the bar, and the striker got in before the green-shirted opposition players to force the ball over the line. Barney would later be carried off on a stretcher though, after suffering an ankle injury which Neil Baker later confirmed looked like a "bad one".
Slough never looked back after the second goal. Full of confidence, the Rebels went close to extending their lead before the interval and started the second half in much the same vein.
After Sean Fraser was cautioned for conceding a foul 20 yards out, Biggleswade's big striker Inih Effiong went close with a well-struck free kick which hit the bar and rebounded to safety, and later Effiong brought a good save out of Mark Scott after Parker had struck the ball goalwards from a short corner.
But the Rebels, with the superb Lee Togwell anchoring midfield and keeping his side ticking, remained firmly in control. Dobson volleyed over the bar and later whipped in a fierce free kick which Brown held, with James also curling a shot just over from the edge.
It wasn't all good news for Slough as Barney's match ended prematurely due to an ankle injury, sustained as he slipped when chasing a long pass forward. The striker looked likely to beat goalkeeper Brown to the ball in a straight race before collapsing in agony.
After a break of around five minutes due to the injury, Scott was alert to dive at Effiong's feet to snuff out the danger, and then in the final minute Slough made sure of the points as Gavin James tapped in Dobson's low cross from close range.
Biggleswade Town Line up
Ian Brown, Harry Norman, Lucas Perry, Russell Short, Gavin Hoyte, Robbie Parker, Craig Daniel (c), Connor Hall, Inih Effiong, Ian Rees, Chris Marsh. Subs: Alan Key, George Bailey, Callum Lewis, David Clifton, Connor Vincent.