Selby led 6-2 overnight and soon extended that to 10-2 today with top breaks of 96, 58 and 66. Williams pulled one back with a run of 79
Neil Robertson wins second title of the season following his success at the Uk Championship.
John Higgins beat Ronnie O'Sullivan 6-3 in the quarter-finals of the Masters.
John Higgins also advanced as he beat Jak Jones.
The world number 66 produced a thrilling display of attacking snooker.
Indoor sporting events in tier one and two locations are conceivably able to host a maximum of 1,000 fans under Covid-19 regulations.
O’Sullivan chalked up three half-century breaks and a clearance of 121 in a near faultless display at the Marshall Arena.
Stuart Bingham also compiled the second maximum break in as many days in the sixth frame of his first-round win over Zak Surety.
Kyren Wilson had a break of 147 on Tuesday.
The Englishman follows in the footsteps of Judd Trump, who made a maximum en route to winning the Northern Ireland Open last week.