Hello, my friend! I only started working on comics recently myself but I hope that helps! Good luck with yours!!
I’m sure you may find some tutorials on speech bubbles online; the borders around the panels are exaclty like speech bubbles - just long white strokes with strokes added with Photoshop
(the size shown in the corner of second-to-last artwork is the size of the whole page, not of this panel)
also if anyone’s asking; the page is from The Hourglass, a joint project between me and gloriousmonsters