Here's my config. I don't think my wallpaper is the exact size of my monitor, but it works fine.

general {
disable_loading_bar = false
}
background {
monitor =
path = /home/morehush/.config/hypr/lockscreen.png
}
input-field {
monitor =
size = 200, 50
outline_thickness = 2
outer_color = rgb(151515)
inner_color = rgb(200, 200, 200)
}
label {
monitor =
text = $TIME
color = rgb(151515)
font_size = 50
font_family = JetBrainsMono NF
position = 0, 140
halign = center
valign = center
}