If anyone who uses i3 needs an fzf application launcher in their lives, adding the following two lines to your config will make $mod+d open it as a floating window in the middle (uses rxvt-unicode):

    bindsym $mod+d exec --no-startup-id urxvt -title "fzf-menu-random123" -e bash -c 'i3-dmenu-desktop --dmenu=fzf'
    for_window [title="fzf-menu-random123"] floating enable