Try the spell

With their soles still pressed together, Jane starts to read the spell out loud.

"Et vestigia pedum coniungere.."

"J- Jane, I think I'm starting to feel something.", said Mary.

"Woah, yeah. Me too.", replied Jane.

There was a feeling of warmth between their skin. From what was sweaty and wet, suddenly turned slightly sticky and hard.

Both Mary and Jane tried to separate parts of their feet, but it seems their skin were adhering to each other faster than they could pry them apart.

"Oh my, it- it's actually working!", said Mary in a surprised manner.

"A- oh.." Jane couldn't even say anything as the feeling was overwhelming.

Their line between their skin started to fade away as it melded together. From their heels all the way to the balls of their feet.

After the feeling died down, both Mary and Jane went to check their feet. Mary running her fingers along where a seam between their feet should be.

"Uhm.. Jane, I think it worked. I can't tell where my feet even end.", Mary, slightly nervous, said to Jane.

"Oh it definitely worked.", replied Jane.

"D-did it say how long this would last?", asked Mary.

Jane looks around for the spellbook, but notices it closer to Mary.

"Hey, maybe you could check it. The book's much closer to you."

"Okay, hold on I'll check.", replied Mary.

Jane inspects their feet even further.

"You know.. This kinda feels nice actually.", said Jane.

"Yeah, I guess it does."

"Would be kind of a bummer if we just ended it as soon as we started." said Jane, in a slightly joking manner.

"I wouldn't mind being stuck together for a while longer. After all I didn't really have much plans today."

Jane and Mary move their feet. They really were fused at the soles.

"Well, what do you want to do Jane?", asked Mary.