“Show, don't tell” doesn't apply to this individual. If you don't tell your lover you love them, they won't feel loved.
This isn't insecurity; everyone feels love differently. "Words of affirmation" people need to hear your sentiments.
Complements are never excessive.
Write your words on important events. A genuine card or letter with a few phrases about why you love them will be treasured and read hundreds of times.
If you're not a wordsmith, your spouse doesn't need fancy words. You're loved. They want your opinion, even if it's not well-spoken.
Praise your companion regularly in their interests. Tell writers what you like. Applaud their housecleaning efforts. Tell them whether they look well that day. Start saying good thoughts out loud.
Express yourself on significant occasions. Add some text to store-bought cards.
Send them an unexpected message a couple times a week to let them know you love them or are thinking of them. Think about how you want your lover would speak to you in your love language all week.
Uplift your companion. Listen without interfering. Remind them of their strengths to help them get through this.
Saying "I love you" too frequently never ended a relationship.
Be honest. Words of affirmation partners need loving words, but not phoney ones. Insincere remarks might be worse than none. Just be honest.