When I add the entity in the lovelace it only gives me a temperature Icon and not the value.
When trying to add a template sensor it gives med the following error.
Invalid config for [binary_sensor.template]: [unit_of_measurement] is an invalid option for [binary_sensor.template]. Check: binary_sensor.template->sensors->pooltemp->unit_of_measurement. (See ?, line ?).
You can use the header or footer abilities. It might not look the way you like though. Otherwise you can investigate using picture-elements card to position items where you want them.