Second this. I have the same setup. I considered circumventing the timer, but decided against it for safety and energy savings protection.

Hardware list for a 6kW heater: (As AudioVoodoo mentioned, size amperage ratings for your application accordingly)

IF YOU HAVE ANY DOUBT, CONSULT/HIRE AN ELECTRICIAN

Packard - DP301202 C230B 2 Pole 30 Amp Contactor, 120 Voltage Coil Amazon link

Smart Light Switch Apple Homekit - Refoss Single Pole Smart Switch Wi-Fi Wall Switch Compatible with Siri, Alexa & Google Assistant, Remote Control Amazon link

Ogrmar Plastic Dustproof IP65 Junction Box DIY Case Enclosure (8"x 6"x 4") Amazon link

TayMac MM7440C Two-Gang Weatherproof in-Use Cover, 55-in-1, 2, Clear Amazon link

GFCI Outlet 15 Amp, Tamper-Resistant, Weather Resistant Receptacle Indoor or Outdoor Use, UL Listed, LED Indicator with Decor Wall Plates and Screws Amazon link

Edit: Links only for convenience, no affiliation to Amazon or any of the products.