In the aftermath of the Seahawks’ stunning 43-8 demolition of the Denver Broncos in Super Bowl XLVIII, it sure seemed like the foundation of a dynasty had been laid.

A year later, sitting on the goal line at the end of Super Bowl XLIX, the Seahawks were poised to finish off the second floor of the three-story dynastic castle. But coaching mistakes ruined their first shot at that rare achievement.

First, Pete Carroll allowed Darrell Bevell to make the worst play call in Super Bowl history, and then Carroll followed it up by fielding a ridiculously overmatched offensive line in a stunningly underachieving 2015 season.

When you raise expectations the way Carroll and John Schneider have over the past four years, anything short of winning it all is total failure. The Seahawks were primed to become one of the league’s rare dynasties, and they screwed it up.

Now, as they begin Part III of the PJ Era, they think they can quickly recapture the spirit of 2013 and return to the Super Bowl.

“I think it’s very close,” Schneider told John Clayton at the league meetings last week. “Obviously, we feel like there’s a number of things we need to take care of still. We always feel like that. It never ends. We never feel like we have all the answers or have everything figured out. But just our core group of guys, I think, is very strong.”

It should remain so for at least the next two or three years, with seven starting defenders and five starting offensive players signed through 2018.

But Schneider’s work the rest of this offseason will determine just how Super the Seahawks can become this year and beyond.

They have gone 6-5 with their free agents so far, replacing three of the five losses with “role players,” as Schneider called J’Marcus Webb, Bradley Sowell and Sealver Siliga.

Seattle’s big additions are likely to come in the draft, but they are not necessarily finished in free agency. As Schneider said, “We’re still in the process, to a certain extent.”

At this point, the Hawks likely are just looking at players who have been released from other teams. One key player they might check into before the draft is former Giants left tackle Will Beatty, who is about ready to work out for teams. Veteran guards still available after being released include Louis Vasquez, Jahri Evans and Ben Grubbs. Other tackles who still could be released include Ryan Clady (Denver) and D’Brickashaw Ferguson (Jets).

The Seahawks also could still look at center Stefen Wisniewski, if he remains unsigned after May 12, when he would no longer count in the compensatory equation.

Whatever they do, Schneider made it clear: “We’re going to be continuing to tinker our way through free agency here a little bit with the offensive line — and obviously the draft.”

We won’t know the full makeup of that unit until after the draft — possibly into mid-May. But Carroll and Schneider know it is the one weak link that needs to be fixed before the season begins.

If they address it properly, the Seahawks will have another shot at establishing the dynasty they failed to create in Part II of the PJ Era.

Some are concerned Carroll and Schneider might not stick around for all of Part III, but Schneider allayed any of those worries when he said, “We are just going to keep staying together and keep doing what we are doing and see how long we can make it last.”