If I were in your situation, I would just show the ones from grad school that were first author. You should have a few from the last year or two of the degree and they may have even come out after you left.
I would not enclose the non-FA papers. Don't open that box. (But of course show them on your CV, since that has everything.)
And I would not have spent a postdoc, not getting recent first author papers. As you can see they would be desirable, now.
Of course, if you get to an interview and are asked about it, have a practiced poised answer ready. [Standard interview prep for any job interview is to write out 2-3 sentence canned answers for anticipated questions. Especially important for weak areas, since you just want to give a forthright but short answer and move on. And if you think about it ahead of time, this works much better.] But don't enclose as select examples, work where you were not FA, if at all possible.
When they ask for select papers to attach, they probably just mean a couple. Won't read more than that. So use selection and pick the best ones. And those are not going to be second author ones if first author ones are available. In other words, when they ask for your recent work, there are two conditions: "your" and "recent". And (I assert) "your" is the more fundamental, important criterion.
And of course if you don't have any FA papers even from grad school, enclose what you have. It's not ideal. But it's what you got. So just plow ahead.