Overlapping String-Blocks
JavaScript (Node.js), 24 bytes

Saved 2 bytes thanks to @Grimy

Assumes that the returned string is printed on a terminal that supports ANSI escape codes. Contains the unprintable character ESC, which is escaped (no pun intended) as \x1B below.



a=&gt;`\x1B[2J\x1B[H`+a.join`\x1B[H`


This doesn't work on TIO, but you can Try it online! to see the raw output instead.

How?

The CSI sequences used are:


ED (Erase in Display):

ESC[2J

where \$2\$ means "clear entire screen"
CUP (Cursor Position):

ESC[H

which means "moves the cursor to row \$n\$, column \$m\$" where both \$n\$ and \$m\$ are omitted and implicitly set to \$1\$ (top-left corner of the screen).


Example output