By the Grace of the Gods (manga)

By the Grace of the Gods (神達に拾われた男; "Kamitachi ni Hirowareta Otoko") is a manga series based on the novel of the same name.

Official Synopsis
Under the protection of the gods, a relaxed life with slimes in another world begins! One day, the life of middle-aged Japanese businessman Ryoma Takebayashi came to a rather sudden and disappointing end. Ryoma had never had a blessed life, but after his death, three great gods sought his cooperation and reincarnated him as a child in another world with swords and magic! Receiving a most cordial and divine welcome from the gods, Ryoma decides to live leisurely on his own in the forest for the time being. Working diligently at magic and hunting, Ryoma’s greatest passion comes to be researching his tamed slimes?! Training a variety of slimes (some newly discovered), the curtain rises on this easygoing life fantasy celebrating a second life with kind people in another world! Source: J-Novel Club